The reliability for measure and control system of a space environment simulator is analyzed in the paper to build the models. The paper systematically summarizes the state of measure and control system. The system structure and principles are introduced. According to requirement of environmental test, working procedures of the system are divided into the particular assignments. On the basis of reliability theory, reliability block diagrams and corresponding mathematical models of the assignments are presented. Meanwhile, the critical factors are analyzed in the paper. By the research on reliability of the system, the scientific bases are provided for the system improvement in the future, which could enhance the reliability and safety of measure and control system.