With the rapid development of computer technology and the application of supercomputers, digital simulation technology has become more closely integrated with the design process of nuclear power plants. The CONST (CONtainment and Safety system Test facility) is an integrated thermal–hydraulic facility designed for the safety system of third-generation reactor AHPR1000. In order to achieve the rapid iteration analysis and optimization of the operation scheme of the test facility, reduce the construction and maintenance costs of next step of the test facility modification, this article developed a simulation platform for the CONST based on the VITARS platform and RELAP5 program, including functions such as operation control, parameter interaction, and case management. The platform simulates systems including the primary circuit system, safety system and other auxiliary systems. All simulation parameters are derived from the actual design and operation parameters of facility. The platform is connected to the DCS virtual machine system of the test facility and achieves semi-physical interaction between the simulation platform and the DCS. After testing, the simulation platform can achieve the integral simulation of the test facility and can be started and stabilized through the DCS virtual machine system, which can meet the requirements of operation simulation. The simulation platform achieves the analysis and optimization iteration of the operation process of the physical facility and can function well in parameter analysis of the subsequent operation and in modification verification work.