The invention discloses a method for preparing a micro electro mechanical system (MEMS) structure, which comprises the following steps of etching a peripheral area on the front surface of a substrateto form a plurality of parallel second grooves, depositing and forming a piezoelectric composite vibration layer on the substrate, wherein the piezoelectric composite vibration layer formed at the bottoms and the side walls of the second grooves forms a first corrugated part; depositing and forming a mass block in the middle area of the piezoelectric composite vibration layer; etching the exposedsubstrate outside the piezoelectric composite vibration layer to form a first groove; etching the back surface of the substrate to form a cavity, wherein the first groove is adjacently arranged at theperiphery of the cavity, the piezoelectric composite vibration layer is formed right above the cavity, and part of the substrate located between the first groove and the cavity supports the piezoelectric composite vibration layer. According to the MEMS structure manufactured by the method, the displacement and the deformation of the piezoelectric composite vibration layer under the action of sound pressure are improved, the residual stress is reduced, and the sensitivity of the MEMS structure is further improved.