In this paper, with dynamics analysis on whole vehicle and hydraulic retarder, the dynamic simulation model of engine and hydraulic retarder continual braking on sloping hillside of tracked vehicle is built by using Simulink software. The simulation results show that when engine and hydraulic retarder continual braking is used opportunely, it can meet the demands for tracked vehicles to safely travel on sloping hillside with constantly velocity, and it can extend the service live of mechanical brakes.