The principle of suspension of bearingless permanent magnet synchronous motor (BPMSM) was analyzed. A set of damping coil was added on the rotor, and an accurate mathematical model of radial suspension force for BPMSM was established. The mathematical model was calculated, compared and analyzed. The results showed that the stability of the rotor was enhanced. By using rotor magnetic field directional control strategy, the control system of BPMSM was designed and constructed. Then the displacement of the rotor and other parameters was simulated. The simulation results showed that the stability of the motor and the robustness could be improved effectively after adding the damping coil.