Using the large-amplitude elongated-body theory and the calculation formula of the drag force of the robotic fish improved in this paper, the dynamics model of the plane motion of the robotic fish was built. Then, a 3D simulation model of the robotic fish based on ADAMS is established, at the basis of which, a simulation was made to analyze the influence of the kinematics parameters to the cruising velocity and the swing angle of the robotic fish body. The simulation result shows that the dynamics model established is reasonable and effective, and the simulation analysis provides the theoretical basis for the design and study of the robotic fish.