Power control unit (PCU) is an important component of space power system on satellite; it provides power supply to main bus and regulates output status of solar battery array in light district. So it is very important to test the performance of PCU before equipped in satellite. A semi physical test system for PCU is developed in this paper, some Agilent simulators are used to simulate working environment of PCU, and control software is programmed to control these simulator as well.