This paper presents a simulator for a video processing circuit system of satellite cameras, which fulfills test requirements of each part of circuits of the video process system before being assembled. The simulator can generate simulated video digital signals, control signals of the camera management controller, and image the digital signal of the information processor. FPGA was adopted to act as a center unit, the logic of the simulator is developed with VHDL, The RS232 interface is used to receive instructions from the host computer and simulate telemetry and telecommand. Test results show that the simulator can fully conduct testing of the imaging circuit system and can shorten the debugging time. It is a very important equipment in development of the video process circuit system.