Abstract: To facilitate the astronauts extravehicular activities, and improve the system reliability, the SIMATIC PCS7 redundant distribution control system is adopted in the assistant KM6 device to simulate thermal and vacuum environments in space. In the control system, the key parts, including control computer, CPU, power supply, network, I/O module, are backed up. The redundant functions in the control system, the implementations and the measurement principles are discussed. With the application of the system in the KM6 horizontal chamber, the reliability and stability of the control system are enhanced greatly.