The working principle of hydrostatic driving loop of mountain tractor is briefly introduced. The hydrostatic driving loop of mountain tractor was modeled by AMESim and the corresponding action curve was obtained by simulation and analysis. The effects of different damping holes, different spring stiffness of directional valve, different moment of inertia of load, different displacement of main pump and different displacement of driving motor on the dynamic characteristics of hydrostatic driving loop of mountain tractor were analyzed. The obtained result provides some references for the practical design, selection and application of hydrostatic driving loop for mountain tractor.