Aimed at the sealing failure of drive shaft assembly of impact positive displacement motor under the coupling of high temperature threedimensional compound motion (reciprocation + rotation),the heat aging test of hydrogenated nitrile butadiene rubber was designed.Based on the data of thermal aging test,the threedimensional finite element model of O-ring seal of drive shaft assembly of impact positive displacement motor with thermal aging effect was established.The finite element method was used to study the influence of fluid pressure,temperature,friction coefficient and reciprocating velocity on the static and dynamic sealing performance of O-ring.The results indicate that under the static sealing condition,the high stress zone is located on the right side of the O-ring,the high contact pressure zone is located on the inside contact surface,the side contact surface and outside contact surface of the O-ring,the maximum von Mises stress and the maximum contact pressure are increased with the increasing of fluid pressure and temperature,and the maximum contact pressure is decreased with the increasing of friction coefficient.Under the dynamic sealing condition,the maximum von Mises stress and the maximum contact pressure have abnormal regularity when the reciprocating velocity is 0.4 m/s and the friction coefficient is 0.25,and the maximum von Mises stress and the maximum contact pressure are increased with the increasing of fluid pressure and temperature.Therefore,it is suggested that the sealing ring should be operated in a reciprocating speed less than 0.4 m/s and a small friction coefficient under the static and dynamic sealing states.