A pulse tube refrigerator is manly for cooling sensors in satellite.It is also important for ground using.A displacer pulse tube is one of the revisable pulse tube refrigerators which can operate at cold engine model to generate power by using the cooling energy of cooling sources such as LNG.A nodal analysis numerical model is used for the simulation of the cold pulse tube engine with the cooling energy of LNG.The basic working mechanism of the cold pulse tube engine is explained.It is shown that the optimum swept volume ratio of displacer over expander changes with the length of the pulse tube

the power of the cold pulse tube engine can be adjusted by the swept volume of the expander.