Abstract: A troubleshooting system for electric vehicle is described. It is developed by OOT (object oriented technology). It is convenient for a programmer to analyze and design the troubleshooting software by the method of OOT. The troubleshooting system can monitor the status of the main electrical parts of electric vehicle, such as traction motor, controller, and traction batteries etc. The system can check troubles as soon as possible if they occur. The system can enhance the reliability and self maintenance of electric vehicle. The software can be updated easily by means of OOA/OOD (object oriented analysis/object oriented design).