Based on generalized Reynolds equation of average flow model,the comprehensive oil film thickness expression considering the shape error of engine main bearings was derived.A lubrication analysis calculation model for the main bearings of the internal combustion engine was established with considering the shape error mainly including straightness error and circularity error,and the influence of the two kinds of shape errors existed in journal and bearing bush on lubrication performances of main bearings was studied.The results show that the same type shape errors with different kinds of tessellation lines has greatly different influence on lubrication performances of main bearings,and compared with the ideal journal,the shape errors result in the increase of oil film pressure and friction power loss and the decrease of minimum oil film thickness.The linear peak has significant effect on lubrication performances of main bearings,and the linear symmetry is beneficial to improve the journal misalignment.The shape errors of journal and bearing bush have a coupling effect on lubrication performances of main bearings,the difference in direction of two shape errors causes the increase or decrease of oil film thickness in different place.The influence of shape errors on lubrication performances is significantly different in different working conditions,with the increase of rotational speed,the influence on lubrication performances by shape errors is aggravated,the maximum oil film pressure is increased,the minimum oil film thickness is decreased and the total friction power loss is increased.