Abstract: A simulation scheme based on the platform of MATLAB software for the high/low temperature environmental simulation system (H/L TESS) is introduced and illustrated by an example of simulation project. Fist the MATLAB simulation models library of the system is built for systematic simulation purpose with the individual equipment as basic module, the equations such as state equation, mass continuous equation, energy conservation equation, momentum conservation equation, etc. as the foundation, and the MS-Function and masked block as the basic method. Then the simulation models of a real environmental simulation system are set up using the models of this library. And last the application software of the H/L TESS is developed by the technology of MATLAB graphics, ActiveX data transfer and dynamic data transfer. It is approved that the approach can effectively carry on planning and design of system simulation research and give both the research and the application software a good continuity and expansion.