In order to verify the performance of the designed temperature controller of the plastic extruder using supercritical CO2, we developed a Hardware-In-the-Loop (HIL) simulation system based on Matlab/Simulink RTW. In this platform, data transmission between real process and Matlab workshop was carried out by the data acquisition cards supported by xPC Target, so that the physical system was integrated to the simulation loop, and the system modeling, analysis, digital simulation and target downloading were all realized. The result showed that the designed temperature control algorithm had better effect when used in the plastic exturder production field. This HIL simulation system can shorten the development cycle and cost, improve the design level of the control system, and provide a solution to the demonstration of the controller in the real-time mode. What’s more, this simulation system can be applied in other process control fields as flow, pressure, etc.