When the plunger pump is running at high speed and high pressure,there is often a certain inclination angle between the plunger and the cylinder body,which causes friction and wear or plunger jamming of the plunger pair,seriously affecting its service life.To study the effect of plunger deflection on the lubrication and leakage characteristics of plunger pairs,the influence factors of pressure and shear flow were introduced to correct the Reynolds governing equation of the clearance flow,the oil film thickness equation considering the deflection of the plunger was established,and the lubrication and leakage characteristics of the plunger pair were analyzed using finite element method.The results show that the inclination angle of the plunger has a significant influence on the lubrication characteristics of the plunger pair,the maximum oil film pressure of the tilted plunger increases significantly,while the minimum oil film thickness decreases significantly.When the inclination angle is 0.000 15°,the lubrication state inside the plunger pair transitions from elastohydrodynamic lubrication to mixed lubrication,and when the inclination angle is 0.000 25°,the maximum oil film pressure is about 14 times that of non inclination.The inclination angle of the plunger has slight effect on the leakage characteristics of the plunger pair.As the pressure difference between the two ends of the plunger pair increases,the leakage ratio of a single plunger pair increases approximately linearly.When the contact length is small,the leakage volume is large and the slope of the vary curve is steep.When the unilateral clearance increases to a certain value,the leakage ratio increases significantly.The research can provide references for the plunger pairs precise theoretical design and the instability of the core rotating components of aviation piston pumps.