Abstract: In this paper, a new structure was studied for the inner and outer meshing gear motor. It took a double stator principle to change the original structure of the gear motor, so as to implement the adjustment of rotational speed in gear motor without changing the input flow rate. The difference between the new structure and the traditional gear motor is that there are one internal gear motor and one external gear motor in one shell, and multistage speed and multistage torque output can be achieved only with switching different connection. The new motor leaves out some components, such as throttle valve, pressure reducing valve, reducing the energy dissipation and improving the motor efficiency.