Affixing inverse magneto-elastic material on the CD-shaped rotor（turn plate）of ultrasonic motor is an original approach that realizes the non-contact torque measurement of rotating shaft.Due to the characteristics that ultrasonic motor produces no magnetic field

it ensures the reliability of torque measurement.CD-shaped rotor magnifies the torque in shaft

which improves torque measuring precision and range

and saves much space with the benefit of alleviating the difficulties of implanting torque measuring device inside the ultrasonic motor in the future.Experiment shows that the presented toque measuring method archieves torque measurement and variation detection with strong stability and anti-interference capability.