Abstract:The function and basic principle of underground diaphragm wall hydraulic grab control system were analyzed. With the theory of power bond graph, the bond graph model of the system was established. Independent variable's integrations of capacitive element and inertial element were selected as state variables and state equations of were deduced. Simulation results based on MATLAB prove the control system has very excellent characteristics. Lastly, the influence of changed parameters to the system was also discussed.