Aiming at the need of continuous and stable power supply for vehicle sensors during driving, a new piezoelectric energy harvester consisting of the main resonant cavity structure as the main body and a spoiler cylinder and Helmholtz resonant cavity as auxiliary is designed in this paper. To study the power generation performance and design optimal structure, a fluidsolidelectric coupling simulation model is established. In the simulation, the wind pressure load is applied to each part of the piezoelectric generating module according to the actual wind pressure distribution. The simulation results show that the thickness ratio of the substrate to the piezoelectric ceramic has an effect on the output voltage and natural frequency of the piezoelectric cantilever beam, and the optimum thickness ratio is 1.25 to gain the optimal power generation 〖JP〗performance, There are optimal size parameter in the gap between substrate and main cavity, the spoiler cylinder diameter, and the Helmholtz resonator to optimize the power generation performance of the piezoelectric energy harvester. When the load resistance is within 400~600 kΩ, the optimal output power will be obtained, while when the wind speed is 15 m/s, the maximum output power reaches 373 mW.