Abstract:One online test system is designed to monitor Single Event Effect(SEE) of Vertical Double-diffusion Metal Oxide Semiconductor(VDMOS) Field Effect Transistor(FET) device. The hardware structure of the test system is described in detail from the aspects of the design of the offset, the acquisition of the waveform, the control and the remote monitoring after briefly introducing the experimental principle. Then the design flow of the software and the operating interface of the test system are given. In the end, experiment is completed by using the automatic test system, and the results are obtained. It is proved that the system is stable, reliable, portable and easy to use.