今天我也遇到了同样的问题，我走过了下面这条路—— (%USERPROFILE%\AppData\Roaming\npm)，当我清除npm目录下的所有内容时，才知道有一些垃圾数据。现在当我运行(npm安装命令再次)。现在一切正常。

NPM install -g @angular/cli代替了NPM install @angular/cli

通过命令

npm install -g @angular/cli@latest

它工作得很好，我现在能够运行ng命令了。

关闭CMD并再次以管理员权限打开或重新启动系统。

I was having the same issue when tried with the syntax "ng new " and solved that simply by updating the existing node version from 5.x.x to 8.x.x. After successful updation of node, the syntax worked perfectly for me. Please update the existing version of node. As it is clearly mentioned in angular documentation that these commands require the node version >= 6.9.x. For reference please check https://angular.io/guide/quickstart. It clearly states "Verify that you are running at least node 6.9.x and npm 3.x.x by running node -v and npm -v in a terminal/console window. Older versions produce errors, but newer versions are fine".

将新路径设置为c:\ users \你的名字\ appdata \漫游\npm\node_modules\@angular\cli\bin\ng现在对我来说很好