网上找到的,我没试过.
http://www.fettesps.com/how-to-remove-com-ports-which-are-in-use/

C:WindowsSystem32Command

    Enter set devmgr_show_nonpresent_devices=1 into Command Prompt
    Open Device Manager
    Click View -> Show Hidden Devices

Now when you expand the section on COM ports, the non present COM ports will be in grey. You can now easily remove any unwanted devices that are tying up COM ports by Right Clicking then selecting Uninstall. After you are done, should you wish to hide these devices again you can do so by entering
set devmgr_show_nonpresent_devices=0 in Command Prompt.