Based on the theory of elastic hydrodynamic lubrication,bearing dynamics and balance ratio calculation,taking into account the effects of the surface roughness of the journal and the bearing shell,the elastic deformation of the crankshaft and the bearing housing,a lubrication analysis and calculation model for the main bearing of 12 cylinder V150 diesel engine was established for the crankshaft system of a highpower diesel engine.The lubrication performance of each main bearing of the 12 balance weight crankshaft at different balance rates was analyzed,and considering the parameters of bearing width,bearing clearance and oil supply pressure,the crankshaft with better balance was optimized.The results show that with the increase of equilibrium rate,the minimum oil film thickness is increased first and then decreased,the maximum oil film pressure and average friction loss are decreased first and then increased,and the crankshaft with balance rate of 80% has better lubrication performance.But the minimum oil film thickness of main bearings MB5,MB6 and MB7 is less than 1μm.After optimization,the lubrication performance of each main bearing meets the requirements,the minimum oil film thickness of the main bearing MB7 with the worst lubrication is increased by 19.7%,and the maximum oil film pressure is decreased by 11.8%.