The design of ECU automatic test system based on virtual Instrument was discussed. Using a variety of high precision cards to simulate senor signals of the ECU and output load of ECU was also simulated in this system. Simultaneously, the ECU was monitored via CAN communication. In part of software design, choosing TestStand as test management software, and using subVI written by LabVIEW as step of sequence in the form of module for testing. At the end, the test results of system were analyzed to verify the reliability and stability of the system. 