According to its mission，underwater vehicle is usually loaded with different combat payloads，and the lid opening process during vehicle rising is a key action flow in its combat process. The underwater vehicle system is affected by wave force，rocket thrust，gravity，fluid resistance and other factors during its working process，and its lid opening process generates relative motion between the components，which makes its motion characteristics complex. The dynamic equation of the underwater vehicle system is established based on Kane method. The mixed coordinate method is selected to describe the position relation of rigid bodies. The motion response of underwater vehicle under different load cases is calculated and the factors affecting the lid opening process are analyzed. The results show that increasing the thrust force or the piston stroke of thruster can obviously shorten the time of lid opening process. The lid opening process has little effect on the motion of underwater vehicle，thus it can be ignored. The higher the barycenter position of the lid is，the shorter the time to reach the angular velocity inflection point is，and the more beneficial it is to open the lid. When the initial inclination angle of the underwater vehicle is consistent with the rotation direction of the lid，the time of lid opening process can be shortened obviously. The inclination angle of the underwater vehicle has little influence on the thruster.