Considering the influence of front piston annular gap,the Stirling engine piston seal structure model of flow resistance was established,and the static and dynamic numerical calculation was carried out.The relationship between pressure and flow rate in each sealing part of piston was obtained,and the flow characteristics of the working medium changing with the structure parameters was analyzed.The results show that the dynamic and static flow resistances of the piston seal show different characteristics,with the increasing of flow rate,the dynamic flow resistance is increased,and the static flow resistance is a constant.The piston ring leakage area has a large influence on flow resistance,a composite piston ring can be used to increase the flow resistance and reduce the leakage.The front gap width has a small influence on flow resistance,the friction of piston and cylinder can be reduced by increasing the gap width without affecting the piston seal.