The multi-body dynamics model with rigid-flexible integration of the mechanical-hydraulic governor of diesel was set up based on the theory of computational dynamics of multi-body system. The initial conditions and boundary conditions were analyzed and added correctly to the components of the model. Then the working process of the mechanical-hydraulic governor was simulated, and the dynamic characteristics were analyzed. The results show that the model and the solving process are correct and credible. These pave the way for the further study about structure and capability optimum of the speed governing system. The whole analysis process provides a simple and feasible approach which can be used in other mechanical and hydraulic system.