In order to investigate the influence of the port plate pair parameters of the piston pump on the friction performance under the thermal fluid structure coupling,the lubrication model of the port plate pair was established,and the Reynolds equation,energy equation and elastic deformation equation were solved by finite difference method.Considering the effects of viscosity-temperature and viscosity-pressure,the numerical solution of oil film pressure,elastic deformation and oil film temperature distribution under thermal fluid structure coupling were obtained by relaxation iteration method.The nephograms of pressure field,elastic deformation field and temperature field were obtained by MATLAB.The influence of the port plate pair parameters on the oil film carrying capacity,friction,friction torque and friction coefficient was analyzed.The results shows that the inclination angle of cylinder block and the initial oil film thickness have great influence on oil film carrying capacity,and increasing the inclination angle of the cylinder block and reducing the initial oil film thickness can improve the oil film bearing capacity.Decreasing the viscosity of lubricating oil and increasing the initial film thickness can effectively reduce the friction and friction coefficient.