According to the elastohydrodynamic lubrication theory of bearing,combined with finite element and nonlinear multibody dynamics,the lubrication conditions of the crosshead bearing of marine diesel engine were analyzed by considering the effect of friction surface roughness,bearing and shaft neck elastic deformation,oil supply characteristic etc.The results show that in a working cycle,the crosshead bearing is always under compression.The peak value of the bearing load appears at the maximum pressure in the cylinder.The movement track of the axis of the crosshead bearing is always located in a small region of the lower shell.The area of high pressure of oil film is relatively concentrated.There are oil grooves in the lower shell,which reduces the loading capacity of bearing and makes the minimum oil film thickness be small.The asperity contact pressure is small and of short duration with the high smooth degree of friction surface,and the bearing can work normally.In a working cycle,the majority of friction is hydraulic friction power,and the rough contact friction power is relatively small.