The Uninstall wizard allows you to review and uninstall items in your configuration. This wizard is shown when you select items and press Uninstall... from the Installed Software page. To uninstall software from your system:
Click Help > About and then click Installation Details... to open a dialog showing pages that provide more detail about your installation.
Click the Installed Software tab to see a list of the software items that you have installed into your system.
Select the items that you wish to uninstall.
Click Uninstall....
The Uninstall Details page will show you a list of the items that will be uninstalled. Expanding each item will show what additional items (if any) will be uninstalled as a result of your choice.
If you change your mind about which items should be uninstalled, you may click Back to see a checkmark list of the items you selected before. You may check and uncheck different items in the list, and click Next when you are ready to continue. Click Finish to start the uninstall.
Once all of the software is uninstalled successfully, you will be prompted to restart for the Workbench. Click Yes when asked to exit and restart the Workbench for the changes to take effect.
转自：http://stackoverflow.com/questions/369889/uninstall-plugins-in-eclipse-3-4-x