在网上找到解决方案：
Solution
Enable RDP security layer in Group Policy on the machine:
Verify that the firewall allows remote desktop connections with RDP (Port
3389)
Click Start>Run
Type gpedit.msc and click "OK"
Result: The
Group Policy Editor will open
In the left hand side bar, expand Computer
Configuration>Administrative Templates>Windows Components>Remote
Desktop Services>Remote Desktop Session Host
Select "Security"
Change
"Require use of specific security layer for remote desktop (RDP) connection" to
Enabled" and select "RDP" in the Options pane.
Change "Require user
authentication for remote connections by using Network Level Authentication" to
"Disabled."
Close Group Policy Editor and reboot the machine for changes to
take effect.
mac远程桌面连接windows 8.1 update，提示： 远程桌面连接无法验证您希望连接的计算机的身份,布布扣,bubuko.com
mac远程桌面连接windows 8.1 update，提示： 远程桌面连接无法验证您希望连接的计算机的身份
原文：http://www.cnblogs.com/tubo/p/3778517.html