Abstract: Braking conditions are divided into three categories: ordinary braking, emergency braking and inertia braking, then a research about the characteristics of manual transmission(MT) vehicle excellent drivers’ manipulation in different braking conditions is made. The conditions of ordinary braking and emergency braking are classified as deceleration braking, and then begin the study of the automated mechanical transmission(AMT) vehicle. Combined with a heavy off-road vehicle’s parameters and test data, a detailed analysis of the characteristics of Position-type electronically controlled diesel engine is carried out. Then the concept of the natural descending rate of engine speed when throttle is closed is put forward, to slow down or speed up the rate due to external reasons, the engine will produce torque to hinder this movement trends. On the basis of a detailed analysis of the drive system dynamics model of the braking process, the role of engine in different braking conditions is discussed. According to the engine speed and the rate of its decline, the transmission output shaft speed and the rate of its decline, the current gear, clutch state and brake signal, ordinary braking and emergency braking is distinguished, and a shifting control strategy for AMT vehicle in deceleration braking conditions is established. It’s verified by road test in finally.

Key words: automated mechanical transmission, brake conditions, emergency braking, ordinary braking, shifting control strategy