A variable crosssection cantilever beam structure for the piezoelectric energy harvester is proposed in this paper. The finite element simulation analysis of the vibration characteristics and output voltage shows that the proposed structure is beneficial to improve the power generation performance. The fixed end of the energy harvester is a uniform crosssection beam and the freeend is a variable crosssection beam. The piezoelectric layer is adhered on the surface of the uniform crosssection beam. A variety of different forms of variable crosssection cantilever beam can be obtained by changing the width ratio of the freeend to the fixed end of the cantilever beam. The natural frequencies, stress and strain distributions as well as the output voltage response of harmonic excitation of the triangular beam, rectangular beam and the trapezoidal beam with different widths ratio are compared and analyzed. The results show the triangular beam exists higher natural frequency and maximum output voltage. The effects of different variable crosssection range lengths on the output voltage are analyzed. The output voltage of different width ratio energy harvester with the same first order frequency is analyzed, which shows that the output voltage of the unit volume piezoelectric layer of triangle structure is the largest. The output voltage characteristics of the rootbonded piezoelectric patches and the allbonded piezoelectric patches on the base layer were compared and analyzed. The results show that the former has a larger output voltage and better power generation performance.