According to the working principle of hydraulic system and the structure of mechanical parts, the simulation model of a hydraulic excavator mechanical system and hydraulic system was built by using simulationX software. The dynamic simulation of the mining and recovery process of the hydraulic excavator was made. The results show that the system is simple and reliable, and can reproduce the working conditions of the excavator. The simulation results are helpful for optimization design of hydraulic excavators hydraulic system and mechanical system.