In order to realize rotor radial displacement self sensing detection of bearingless induction motor, in this paper, a radial displacement estimation method based on high frequency signal injection method is studied. According to the mutual inductance variation between the torque winding and suspension winding, by injecting fluctuating high frequency voltage signal into torque winding, the induced high frequency current signal in suspension winding is detected, after demodulation to estimate the radial displacement signal of the rotor, and design the rotor radial displacement estimator; then the system simulation verification and analysis of the displacement sensorless control system are made. The simulation results show that the high frequency signal injection method can effectively estimate the radial displacement of the rotor and can realize the motor steady operation without displacement sensor.