The leakage of nuclear power pump is affected by sealing clearance,and the sealing clearance is related with pressure distribution and thermal deformation of the mechanical seal.Based on the basic principles of fluid mechanics and heat transfer theory,the thermalstress coupling deformation analysis model of hydrostatic pressure mechanical seal in nuclear power pump was established.By analyzing the contacting state among the seal rings,the boundary constrained conditions of stator and rotator were obtained.Simulation analysis of face flow field and thermalstress couple deformation of the mechanical seal was carried out in ANSYS software.The simulation results indicate that,within the sealing clearance,the pressure between the inside diameter and turning radius of the seal is approximately linear distribution,while the pressure between the turning point and the outer diameter of the liquid film has a parabolic distribution.The stress of the stator and rotator has a circular distribution,and the maximum stress is at the end surface outer diameter place of stationary ring.The highest temperature in seal rings is near the inner diameter,and the temperature of rotating ring is higher than that of stationary ring.