Abstract: Focusing on the issue of automatic control of starting on the steep slope for heavy-duty off-road vehicle with automatic mechanical transmission (AMT), a test vehicle equipped with AMT and hill-start aid (HSA) system was employed. The characteristics of HSA system were researched and the special demands of steep hill-start were analyzed. Coordinate control between AMT and HSA was adjusted. Then, the auto control strategies were put forward and the software was developed. Vehicle tests have proved the feasibility of this work.