A displacement superposed piezoelectric engaging motor relates to the technical field of piezoelectric engaging motor and overcomes the problems of complicated structure, large volume, low bearing capacity and efficiency, and susceptible to strong magnetic field although the prior piezoelectric engaging motor can direct obtain low rotary speed output. Multiple rectangular through grooves are uniformly opened on the excircle face of an internal tooth elastic wheel. One piezoelectric ceramic body is inlayed to each through groove. A stretchy direction of the electrified piezoelectric ceramic body is parallel to the tangent of the excircle face of the internal tooth elastic wheel. Multiple bulges on the excircle face of the internal tooth elastic wheel are connected to multiple corresponding grooves on the inner circle face of a casing through elastic materials. The internal tooth of the internal tooth elastic wheel is engaged with the external tooth portion of an external tooth rigid wheel. The invention can realize the output with low speed and large torsional moment, and have advantages of simple structure, high energy conversion efficiency, long service life, high reliability, rapid dynamic response, high rotation precision without electromagnetic interference.