Abstract: In order to study fluid flow law of internal chamber in the Stirling engine,and discuss the influence of different conditions,the dynamic grid based on Fluent fluid calculation was adopted to simulate the motion of the dynamic piston and displace piston,the regenerator used the porous media model under laminar flow state,and the standard k-e model was used for other chambers.Within an operating circle,the results show that several vortexes occurred in local area of chambers,which consumed power and decreased engine thermal efficiency and increasing of charge pressure and heater temperature can effectively increase the net output power.