尝试使用:before和:after (ie9+)

#wrapper{
    width:400px;
    height:400px;
    margin:0 auto;
    border: 1px #000 solid;
    position:relative;}
#wrapper:after,
#wrapper:before{
    position:absolute;
    top:0;
    left:0;
    width:100%;
    height:100%;
    content:'';
    background: #1e5799;
    background: -moz-linear-gradient(top, #1e5799 0%, #2989d8 50%, #207cca 51%, #7db9e8 100%);
    background: -webkit-gradient(linear, left top, left bottom, color-stop(0%,#1e5799), color-stop(50%,#2989d8), color-stop(51%,#207cca), color-stop(100%,#7db9e8));
    background: -webkit-linear-gradient(top, #1e5799 0%,#2989d8 50%,#207cca 51%,#7db9e8 100%);
    background: -o-linear-gradient(top, #1e5799 0%,#2989d8 50%,#207cca 51%,#7db9e8 100%);
    background: -ms-linear-gradient(top, #1e5799 0%,#2989d8 50%,#207cca 51%,#7db9e8 100%);
    background: linear-gradient(to bottom, #1e5799 0%,#2989d8 50%,#207cca 51%,#7db9e8 100%);
    opacity:1;
    z-index:-1;
    -webkit-transition: all 2s ease-out;
    -moz-transition: all 2s ease-out;
    -ms-transition: all 2s ease-out;
    -o-transition: all 2s ease-out;
    transition: all 2s ease-out;
}
#wrapper:after{
    opacity:0;
    background: #87e0fd;
    background: -moz-linear-gradient(top, #87e0fd 0%, #53cbf1 40%, #05abe0 100%);
    background: -webkit-gradient(linear, left top, left bottom, color-stop(0%,#87e0fd), color-stop(40%,#53cbf1), color-stop(100%,#05abe0));
    background: -webkit-linear-gradient(top, #87e0fd 0%,#53cbf1 40%,#05abe0 100%);
    background: -o-linear-gradient(top, #87e0fd 0%,#53cbf1 40%,#05abe0 100%);
    background: -ms-linear-gradient(top, #87e0fd 0%,#53cbf1 40%,#05abe0 100%);
    background: linear-gradient(to bottom, #87e0fd 0%,#53cbf1 40%,#05abe0 100%);
}
#wrapper:hover:before{opacity:0;}
#wrapper:hover:after{opacity:1;}

我在工作中使用这个:)IE6+ https://gist.github.com/GrzegorzPerko/7183390

如果使用文本元素，不要忘记<element class="ahover"><span>Text</span></a>。

.ahover {
    display: block;
    /** text-indent: -999em; ** if u use only only img **/
    position: relative;
}
.ahover:after {
    content: "";
    height: 100%;
    left: 0;
    opacity: 0;
    position: absolute;
    top: 0;
    transition: all 0.5s ease 0s;
    width: 100%;
    z-index: 1;
}
.ahover:hover:after {
    opacity: 1;
}
.ahover span {
    display: block;
    position: relative;
    z-index: 2;
}

渐变还不支持过渡(尽管目前的规范说它们应该通过插值支持类似渐变到类似渐变的过渡)。

如果你想要一个背景渐变的渐隐效果，你必须在容器元素上设置一个不透明度，然后“过渡”不透明度。

(已经有一些浏览器版本支持渐变过渡(例如IE10。我在2016年在IE中测试了梯度转换，当时它们似乎可以工作，但我的测试代码不再工作了。)

更新:2018年10月 带有无前缀新语法的渐变过渡[例如径向渐变(…)]现在确认在Microsoft Edge 17.17134上工作(再次?)我不知道这是什么时候加入的。在最新的Firefox和Chrome / Windows 10上仍然不能工作。

更新:2021年12月 在最近的基于Chromium的浏览器中，使用@property的变通方法可以实现这一点(但在Firefox中不起作用)。请在YMMV上方看到@mahozad的回答(并点赞)。

在codepend上发现了一个很好的hack，可以修改不透明度属性，但通过利用伪元素实现从一个渐变到另一个渐变。他所做的就是设置:after，这样当你改变实际元素的不透明度时，:after元素就会显示出来，看起来就像渐变一样。我觉得分享一下会有用。

原始代码来源:http://codepen.io/sashtown/pen/DfdHh

.button { display: inline-block; margin-top: 10%; padding: 1em 2em; font-size: 2em; color: #fff; font-family: arial, sans-serif; text-decoration: none; border-radius: 0.3em; position: relative; background-color: #ccc; background-image: linear-gradient(to top, #6d8aa0, #8ba2b4); -webkit-backface-visibility: hidden; z-index: 1; } .button:after { position: absolute; content: ''; top: 0; left: 0; width: 100%; height: 100%; border-radius: 0.3em; background-image: linear-gradient(to top, #ca5f5e, #d68584); transition: opacity 0.5s ease-out; z-index: 2; opacity: 0; } .button:hover:after { opacity: 1; } .button span { position: relative; z-index: 3; } body { text-align: center; background: #ddd; } <a class="button" href="#"><span>BUTTON</span></a>

我知道这是一个老问题，但也许有人喜欢我在纯CSS解决方案的方式。从左到右渐变。

.contener{ width:300px; height:200px; background-size:cover; border:solid 2px black; } .ed { width: 0px; height: 200px; background:linear-gradient(to right, rgba(0,0,255,0.75), rgba(255,0,0,0.75)); position: relative; opacity:0; transition:width 20s, opacity 0.6s; } .contener:hover .ed{ width: 300px; background:linear-gradient(to right, rgba(0,0,255,0.75), rgba(255,0,0,0.75)); position: relative; opacity:1; transition:width 0.4s, opacity 1.1s; transition-delay: width 2s; animation-name: gradient-fade; animation-duration: 1.1s; -webkit-animation-name: gradient-fade; /* Chrome, Safari, Opera */ -webkit-animation-duration: 1.1s; /* Chrome, Safari, Opera */ } /* ANIMATION */ @-webkit-keyframes gradient-fade { 0% {background:linear-gradient(to right, rgba(0,0,255,0), rgba(255,0,0,0));} 2% {background:linear-gradient(to right, rgba(0,0,255,0.01875), rgba(255,0,0,0));} 4% {background:linear-gradient(to right, rgba(0,0,255,0.0375), rgba(255,0,0,0.0));} 6% {background:linear-gradient(to right, rgba(0,0,255,0.05625), rgba(255,0,0,0.0));} 8% {background:linear-gradient(to right, rgba(0,0,255,0.075), rgba(255,0,0,0));} 10% {background:linear-gradient(to right, rgba(0,0,255,0.09375), rgba(255,0,0,0));} 12% {background:linear-gradient(to right, rgba(0,0,255,0.1125), rgba(255,0,0,0));} 14% {background:linear-gradient(to right, rgba(0,0,255,0.13125), rgba(255,0,0,0));} 16% {background:linear-gradient(to right, rgba(0,0,255,0.15), rgba(255,0,0,0));} 18% {background:linear-gradient(to right, rgba(0,0,255,0.16875), rgba(255,0,0,0));} 20% {background:linear-gradient(to right, rgba(0,0,255,0.1875), rgba(255,0,0,0));} 22% {background:linear-gradient(to right, rgba(0,0,255,0.20625), rgba(255,0,0,0.01875));} 24% {background:linear-gradient(to right, rgba(0,0,255,0.225), rgba(255,0,0,0.0375));} 26% {background:linear-gradient(to right, rgba(0,0,255,0.24375), rgba(255,0,0,0.05625));} 28% {background:linear-gradient(to right, rgba(0,0,255,0.2625), rgba(255,0,0,0.075));} 30% {background:linear-gradient(to right, rgba(0,0,255,0.28125), rgba(255,0,0,0.09375));} 32% {background:linear-gradient(to right, rgba(0,0,255,0.3), rgba(255,0,0,0.1125));} 34% {background:linear-gradient(to right, rgba(0,0,255,0.31875), rgba(255,0,0,0.13125));} 36% {background:linear-gradient(to right, rgba(0,0,255,0.3375), rgba(255,0,0,0.15));} 38% {background:linear-gradient(to right, rgba(0,0,255,0.35625), rgba(255,0,0,0.16875));} 40% {background:linear-gradient(to right, rgba(0,0,255,0.375), rgba(255,0,0,0.1875));} 42% {background:linear-gradient(to right, rgba(0,0,255,0.39375), rgba(255,0,0,0.20625));} 44% {background:linear-gradient(to right, rgba(0,0,255,0.4125), rgba(255,0,0,0.225));} 46% {background:linear-gradient(to right, rgba(0,0,255,0.43125),rgba(255,0,0,0.24375));} 48% {background:linear-gradient(to right, rgba(0,0,255,0.45), rgba(255,0,0,0.2625));} 50% {background:linear-gradient(to right, rgba(0,0,255,0.46875), rgba(255,0,0,0.28125));} 52% {background:linear-gradient(to right, rgba(0,0,255,0.4875), rgba(255,0,0,0.3));} 54% {background:linear-gradient(to right, rgba(0,0,255,0.50625), rgba(255,0,0,0.31875));} 56% {background:linear-gradient(to right, rgba(0,0,255,0.525), rgba(255,0,0,0.3375));} 58% {background:linear-gradient(to right, rgba(0,0,255,0.54375), rgba(255,0,0,0.35625));} 60% {background:linear-gradient(to right, rgba(0,0,255,0.5625), rgba(255,0,0,0.375));} 62% {background:linear-gradient(to right, rgba(0,0,255,0.58125), rgba(255,0,0,0.39375));} 64% {background:linear-gradient(to right,rgba(0,0,255,0.6), rgba(255,0,0,0.4125));} 66% {background:linear-gradient(to right, rgba(0,0,255,0.61875), rgba(255,0,0,0.43125));} 68% {background:linear-gradient(to right, rgba(0,0,255,0.6375), rgba(255,0,0,0.45));} 70% {background:linear-gradient(to right, rgba(0,0,255,0.65625), rgba(255,0,0,0.46875));} 72% {background:linear-gradient(to right, rgba(0,0,255,0.675), rgba(255,0,0,0.4875));} 74% {background:linear-gradient(to right, rgba(0,0,255,0.69375), rgba(255,0,0,0.50625));} 76% {background:linear-gradient(to right, rgba(0,0,255,0.7125), rgba(255,0,0,0.525));} 78% {background:linear-gradient(to right, rgba(0,0,255,0.73125),,rgba(255,0,0,0.54375));} 80% {background:linear-gradient(to right, rgba(0,0,255,0.75), rgba(255,0,0,0.5625));} 82% {background:linear-gradient(to right, rgba(0,0,255,0.75), rgba(255,0,0,0.58125));} 84% {background:linear-gradient(to right, rgba(0,0,255,0.75),rgba(255,0,0,0.6));} 86% {background:linear-gradient(to right, rgba(0,0,255,0.75), rgba(255,0,0,0.61875));} 88% {background:linear-gradient(to right, rgba(0,0,255,0.75), rgba(255,0,0,0.6375));} 90% {background:linear-gradient(to right, rgba(0,0,255,0.75), rgba(255,0,0,0.65625));} 92% {background:linear-gradient(to right, rgba(0,0,255,0.75), rgba(255,0,0,0.675));} 94% {background:linear-gradient(to right, rgba(0,0,255,0.75),rgba(255,0,0,0.69375));} 96% {background:linear-gradient(to right, rgba(0,0,255,0.75), rgba(255,0,0,0.7125));} 98% {background:linear-gradient(to right, rgba(0,0,255,0.75), rgba(255,0,0,0.73125),);} 100% {background:linear-gradient(to right, rgba(0,0,255,0.75), rgba(255,0,0,0.75));} } <div class="contener" style=""> <div class="ed"></div> </div>

2021年:现在可以动画渐变了(Firefox和Safari还不行)

随着Chrome 85, Edge和Opera添加了对@property规则的支持，现在我们可以在CSS中这样做:

@property --myColor1 {
  syntax: '<color>';
  initial-value: magenta;
  inherits: false;
}

@property --myColor2 {
  syntax: '<color>';
  initial-value: green;
  inherits: false;
}

其余都是常规的CSS。 设置变量为初始渐变颜色，并设置这些变量的过渡:

div {
  /* Optional: change initial value of the variables */
  /* --myColor1: #f64; --myColor2: brown; */

  background: linear-gradient(var(--myColor1), var(--myColor2));
  transition: --myColor1 3s, --myColor2 3s;
}

然后，在所需的规则上，为变量设置新的值:

div:hover {  
  --myColor1: #f00;
  --myColor2: yellow;
}

@property——myColor1 { 语法:“< >颜色”; 初值:# 0 f0; 继承:错误; ｝ @property——myColor2 { 语法:“< >颜色”; 初始值:rgb(40,190,145); 继承:错误; ｝ div { 宽度:200 px; 身高:100 px; background: linear-gradient(var(——myColor1)， var(——myColor2)); ——myColor1 3s，——myColor2 3s; ｝ div:{徘徊 ——myColor1:红色; ——myColor2: # E1AF2F; ｝ <div>悬停在我上方</div>

在这里查看完整的描述和示例，并参考这里的@property规范。 @property规则是CSS Houdini技术的一部分。要了解更多信息，请参考这里和这里，并观看这个视频。