It describes an improved numerical model and calculation method for stability simulation of a pulse tube refrigerator.A set of differential equations based on the conservation of mass,energy and momentum for oscillating fluid flow is solved by numerical method.A variety of physical factors,such as actual gas,gas flow friction,heat transfer in the heat exchanger and regenerator,ect.are included to improve the accuracy of the model.The results show the changes of mass flow,pressure,temperature,enthalpy flow and so on in each cell with time.The computer predicted performance is compared with the experimental data.Good agreement has been found between the two.