Abstract: The thermodynamic model of reciprocation type refrigeration compressor including suction cavity, working cavity and discharging cavity is built up, based on the variable mass thermodynamic theory. The kinematic models of suction and discharging valve are set up using Finite Element Method (FEM), and the new method to determine when the valve will depart the limitation ceiling is put forward. Based on this model, the simulation program, which is verified by the experimental results, is made.