添加System.Management的引用，

using System.Management;

string mac = "";ManagementClass mc = new ManagementClass("Win32_NetworkAdapterConfiguration");ManagementObjectCollection moc=mc.GetInstances();foreach(ManagementObject mo in moc){    if ((bool)mo["IPEnabled"])    {        mac = mo["MacAddress"].ToString();    }}

 

参考

http://www.cnblogs.com/diulela/archive/2012/04/07/2436111.html