The stress on the traditional rectangular cantilever beam is not uniformly distributed, for there is a stress concentration area at the fixed end of the beam, which attenuated in the axial direction, thus affecting the polarization effect of the piezoelectric layer. At the same time, the resonance frequency of the energy harvester with the rectangular cantilever beam structure is relatively high. To solve this problem, an energy harvester structure with an “inverted‘ trapezoid structure was proposed, which could effectively expand the polarization region and capture lower-frequency vibration energy. The experimental results show that the output voltage of the energy harvester is 404 mV at 124 Hz, and the output power can reach 41.3 μW with 1g vibration acceleration.