In order to improve the walking stability of amphibious turtle inspired robot, a dynamics model was established, and a force/position control model was proposed based on the PID (proportional integral derivative) feedback control strategy. Firstly, according to the kinematics model of the robot, the transformation matrix and Jacobian matrix of the outrigger were obtained, and a force transfer model between foot end and hydraulic cylinder was established by the virtual work principle. Then, the Lagrange method was used to model the dynamics of the robot, and the dynamics equation of the outrigger was derived. At the same time, the dynamics simulation was carried out, and the real-time force on the foot end was introduced into the dynamics equation for calculation, which verified the correctness of the dynamics model. Finally, a hydraulic simulation model was built, and the robot motion simulation was carried out in the ADAMS?AMESim?MATLAB co-simulation environment. The simulation results showed that compared with the pure position control mode, the rotation of the robot knee joint under the force/position control mode was more stable, and the power output of the hydraulic cylinder was more stable and the power consumption was less. The research results have reference significance for improving the stability of robot motion, enhancing the robustness of motion control system and improving the overall efficiency of hydraulic system.