In this paper，a motion model of the underwater vehicle is established based on the balance equation of the underwater state. Through the numerical simulation calculation of the water hammer pressure，the motion control model of the underwater vehicle during launch is established. According to this mathematical model，the motion response and motion control of the vehicle under the aftereffect of the complete rocket launch(launch impact and complete water hammer effect)are calculated and analyzed. The results show that launch of a single vehicle has a longtime impact on the motion attitude of the vehicle. The greater the initial speed of the vehicle，the smaller the degree of impact and the shorter the impact time. Through steering and the adjustment of the ballast tanks，the motion of the underwater vehicle can be controlled satisfactorily，and the control effect increases with the initial speed within a certain range.
