As a common equipment in the middle and late stages of oilfield exploitation,the seal between the plunger and the pump barrel of the layered oil production pump often adopts a labyrinth seal.Due to the high temperature and high pressure working environment underground,the leakage of seal gap has become the main problem affecting pump efficiency.In order to explore the influence of differential pressure flow and shear flow on seal leakage rate,the simulation experiment of seal clearance flow field was carried out based on computational fluid dynamics and Fluent dynamic mesh technology.The method of grid elastic smoothing and grid reconstruction in dynamic grid was used to avoid grid distortion caused by moving wall surface,and the characteristics of clearance flow field were further revealed.The results show that the shear flow caused by the moving wall is more obvious in the transient simulation.The increase of the shear flow velocity makes the boundary layer thickness thinner,which affects the leakage rate.The gap width,the pressure difference at both ends and the relative plunger velocity have a positive correlation with the leakage rate.The leakage rate is mainly affected by the gap width and the pressure difference flow,and is less affected by the shear flow.