The rectangular cantilever structure is widely used in conventional cantilever piezoelectric energy harvester, due to the width of the piezoelectric plate is constant, the utilization efficiency of the piezoelectric material is limited. A trapezoidal cantilever structure is designed in this paper, in which the cantilever and the piezoelectric layer adhering to it is designed to be trapezoidal. The width of piezoelectric layer is gradually narrowed along the beam length direction. The designed structure is analyzed by the means of theoretical analysis, simulation and experiment. And at the same time a comparison between rectangular cantilever piezoelectric energy harvester and trapezoidal cantilever piezoelectric energy harvester has been performed. The result shows that under resonant state, the stress distribution in trapezoidal piezoelectric layer is more uniform than that in the rectangular piezoelectric layer and trapezoidal cantilever piezoelectric energy harvester has a higher output voltage.