The working principle of piezoelectric vibration energy harvester is described. A piezoelectric cantilever and mass composite structure is proposed to harvest vibration energy in resonance mode, and the mass is added on the edge of the cantilever to decrease the natural frequency of the whole structure. The finite element analysis was carried out on the composite structure using the ANSYS software. The displacement results were obtained by structural analysis, and the first order natural frequency was also obtained by modal analysis. Finally, the influence rules among the structural parameters, such as length and width of the cantilever, length and thickness of the mass and width of the PZT, and the natural frequency, piezoelectric output voltage are discussed in detail. Finally, the optimal structure of the harvester is obtained.