According to the research on the factors affecting the lubrication performance of crankshaft main bearing, a thermoelastic hydrodynamic lubrication model of crankshaft main bearing, considering three different bearing structural parameters, such as journal diameter, bearing aspect ratio and bearing clearance, was established. And the maximum pressure, minimum thickness, maximum bearing temperature, and maximum friction power loss of main bearing under different bearing structural parameters were analyzed. The calculation results show that the structural parameters of main bearing has a great influence on the lubrication performance of crankshaft main bearing. When the journal diameter and bearing aspect ratio become larger, the maximum oil film pressure of the main bearing decreases, and the minimum oil film thickness, maximum bearing temperature and friction power loss will become larger. The bearing clearance will have different effects with the journal diameter and bearing aspect ratio, and the bearing clearance has a significant effect on the maximum temperature and maximum friction power loss of crankshaft main bearing.