一切都很好，但这也应该在env中工作:

PROCESSOR_ARCHITECTURE=x86

..

PROCESSOR_ARCHITECTURE=AMD64

可能太简单了;-)

这只是Bruno Lopez上面建议的一个实现，但适用于Win2k +所有的WinXP服务包。我只是想把它贴出来这样别人就不用亲手卷了。(本可以作为评论发布，但我是一个新用户!)

[DllImport("kernel32", SetLastError = true, CallingConvention = CallingConvention.Winapi)]
public extern static IntPtr LoadLibrary(string libraryName);

[DllImport("kernel32", SetLastError = true, CallingConvention = CallingConvention.Winapi)]
public extern static IntPtr GetProcAddress(IntPtr hwnd, string procedureName);

private delegate bool IsWow64ProcessDelegate([In] IntPtr handle, [Out] out bool isWow64Process);

public static bool IsOS64Bit()
{
    if (IntPtr.Size == 8 || (IntPtr.Size == 4 && Is32BitProcessOn64BitProcessor()))
    {
        return true;
    }
    else
    {
        return false;
    }
}

private static IsWow64ProcessDelegate GetIsWow64ProcessDelegate()
{
  IntPtr handle = LoadLibrary("kernel32");

  if ( handle != IntPtr.Zero)
  {
    IntPtr fnPtr = GetProcAddress(handle, "IsWow64Process");

    if (fnPtr != IntPtr.Zero)
    {
      return (IsWow64ProcessDelegate)Marshal.GetDelegateForFunctionPointer((IntPtr)fnPtr, typeof(IsWow64ProcessDelegate));
    }
  }

  return null;
}

private static bool Is32BitProcessOn64BitProcessor()
{
  IsWow64ProcessDelegate fnDelegate = GetIsWow64ProcessDelegate();

  if (fnDelegate == null)
  {
    return false;
  }

  bool isWow64;
  bool retVal = fnDelegate.Invoke(Process.GetCurrentProcess().Handle, out isWow64);

  if (retVal == false)
  {
    return false;
  }

  return isWow64;
}

完整的答案是这样的(摘自stefan-mg, ripper234和BobbyShaftoe的答案):

    [DllImport("kernel32.dll", SetLastError = true, CallingConvention = CallingConvention.Winapi)]
    [return: MarshalAs(UnmanagedType.Bool)]
    public static extern bool IsWow64Process([In] IntPtr hProcess, [Out] out bool lpSystemInfo);

    private bool Is64Bit()
    {
        if (IntPtr.Size == 8 || (IntPtr.Size == 4 && Is32BitProcessOn64BitProcessor()))
        {
            return true;
        }
        else
        {
            return false;
        }
    }

    private bool Is32BitProcessOn64BitProcessor()
    {
        bool retVal;

        IsWow64Process(Process.GetCurrentProcess().Handle, out retVal);

        return retVal;
    } 

首先检查您是否处于64位进程中。如果不是，检查32位进程是否是Wow64Process。

使用此命令获取已安装的Windows体系结构:

string getOSArchitecture()
{
    string architectureStr;
    if (Directory.Exists(Environment.GetFolderPath(
                           Environment.SpecialFolder.ProgramFilesX86))) {
        architectureStr ="64-bit";
    }
    else {
        architectureStr = "32-bit";
    }
    return architectureStr;
}

使用以下两个环境变量(伪代码):

if (PROCESSOR_ARCHITECTURE = x86 &&
    isDefined(PROCESSOR_ARCHITEW6432) &&
    PROCESSOR_ARCHITEW6432 = AMD64) {

    //64 bit OS
}
else
    if (PROCESSOR_ARCHITECTURE = AMD64) {
        //64 bit OS
    }
    else
        if (PROCESSOR_ARCHITECTURE = x86) {
            //32 bit OS
        }

请参阅博客文章HOWTO:检测进程bit。

我发现这是检查系统平台和流程的最佳方法:

bool 64BitSystem = Environment.Is64BitOperatingSystem;
bool 64BitProcess = Environment.Is64BitProcess;

第一个属性对于64位系统返回true，对于32位系统返回false。 第二个属性对于64位进程返回true，对于32位进程返回false。

需要这两个属性是因为您可以在64位系统上运行32位进程，因此需要检查系统和进程。