Crankshaft main bearing is the key component of internal combustion engine（ICE）, which is used to support the movement of crank link mechanism and realize the conversion of energy. The lubrication performances and wear life of the crankshaft main bearing will directly affect the working efficiency and reliability of ICE. Therefore, it is very important to study the lubrication performances of the crankshaft main bearings. In this paper, a 16V marine diesel engine was studied as the research object. Based on the AVL-Designer software platform, the crank link mechanism dynamics model and the main bearing fluid lubrication numerical model were established. Numerical analysis was carried out on the lubrication performances of the crankshaft main bearings under different rotating speed conditions. The stress state, the maximum oil film pressure, the minimum oil film thickness, the axis orbit and other lubrication performance parameters were obtained from the results. The calculation results show that in the lower half of the central near 180 degrees, the load is larger and the oil film thickness is the smaller. The oil film pressure changes abruptly at the same place, which are prone to wear. The research work provides a reference for the optimal design of the crankshaft main bearings in this diesel engine.