In consideration of the stability and safety in the launch and recovery process of a hybrid autonomous and remotely-operated unmanned vehicle (ARV) in the great depth sea, to eliminate the influence of the heave movement of the mother ship, to prevent cable from being damaged and even ruptured, or ARV from being damaged due to cable's uneven tension, this paper presents a passive heave compensation system that adapts to the launch and recovery of the ARV for "11 000 m" full ocean depth, which was developed by Hadal Science and Technology Center of Shanghai Ocean University. The paper first describes the components of the passive heave compensation system and its operating principle. The oil cylinder dimensions were calculated, then,a mathematical model was established and a simulation analysis of the passive heave compensation system was made using the software AMESim.Numerical calculation and analysis results show that the system can meet the requirement of the launch and recovery of the ARV for full ocean depth. Research of passive heave compensation system has analyzed cable tension control by solving the problem about heavecompensation.