This paper has studied the friction of main bearing on an engine by combining the multi-body dynamics and hydrodynamic lubrication model. First, the basic equations and the application on AVL-Excite software platform of multi-body dynamics have been described in detail. Then, introduce the hydrodynamic lubrication model, which is the extended Reynolds equation derived from the Navier-Stokes equation and the equation of continuity. After that, detailed friction analysis of the main bearing has been performed. The numerical prediction (such as the oil film pressure, the asperity contact pressure and the oil film thickness etc.) was obtained and compared with the experimental data. The result has shown a good agreement between them so as to offer a scientific basis for main bearing design.