The PD test is the main test items for electric equipments insulation, and the partial discharge is the important parameter of electric equipments quality. The detector is based on modularization, designing the simulation parts as standard module according to different function. The modules can be added or deleted as per users requirement. The module is standard Europe type, which is convenient for maintenance and update. It adopts advanced hardware process system, and NI card from America National Instrument. It also adopts digital filtering and other signal process device to collect and analyze the PD signal.