Closed-loop control for underwater heat-engine propulsion system is an essential solution to improve the control performance and optimize the autonomous underwater vehicles (AUV) trajectory. This paper minutely gives the project of the closed-loop control proposal we propose for the propulsion system, and puts forward a control arithmetic according to the mathematical model that has been build for the system. Even more remarkable is that a series of experiments are carried out on the semi-physical simulation test bench to verify the control arithmetic. The experimental results and the analysis indicate convincingly that the control arithmetic can compensate for the navigation depth and attitude of AUV, thus making the propulsion system get the ability of tracking the variable working condition. Therefore, the power system gives full play to its potential.