Focusing on a tracked vehicle auxiliary braking system,modeling and simulation of engine braking were conducted.An optimal control strategy of auxiliary braking was put forward.When there was no hydraulic braking,engine brake force could be used effectively by gearbox shift strategy to reduce the braking force requirements for frictional brakes based on the calculated results of engine braking.When there was hydraulic braking,the braking priority sequence was auxiliary braking,engine braking,and finally frictional braking.A forward simulation model for auxiliary braking system of tracked vehicle was built.The simulation and analysis under typical driving cycles were conducted.The results show that the control strategy and the models are reasonable and feasible.