Engagement control of an automatic mechanical transmission clutch during vehicle start-up has important influences on the safety, comfort, service life, energy consumption, and emissions of the vehicle. However, all existing control strategies use single-layer control, which leads to poor temperature adaptability. This paper develops a double-layer control strategy based on an automatic actuator to improve vehicle start-up performance. The governing characteristics of a diesel engine with a variable-speed governor are studied. The working principles and a model of the automatic actuator are described. A simulation of vehicle start-up is constructed and tested. Finally, the double-layer control strategy is verified in an experimental vehicle. The experimental and simulation results show that the double-layer control strategy provides shorter start times, less jerking, and lower friction, thereby demonstrating its effectiveness and practicability. Keywords: automatic mechanical transmission, start-up process, clutch engagement control, double-layer control Highlights • A double-layer control strategy is designed based on an automatic clutch actuator and controller. • Temperature changes affect clutch engagement performance during the vehicle start-up process. • Comparative outcomes verify the benefits of our scheme in terms of start time, jerking and friction work. • Experiments with an actual vehicle further validate the proposed control strategy.