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A wind piezoelectric energy harvester based on vortex-induced vibrations was studied. The tandem arrangement of two circular cylinders was designed to enhance the amplitude of the pressure fluctuation. The Helmholtz resonator was used for magnifying the wind pressure in the wake region. The flow energy was converted into electrical energy by piezoelectric conversion with oscillation of a PVDF film. The fluid dynamics behaviors of the internal flow field subjected to different wind speeds were analyzed using computational fluid dynamics(CFD) numerical method. Numerical analysis and experimental results showed that the pressure fluctuation in the case of two circular cylinders could reach up to nearly 2 times as that of a single circular cylinder, when the coupling factor L/D=2.2 and subjected to the same wind speed. As the gas in the cavity induced by the oscillatory flow, the gas pressure increased with the wind speed while the vibration frequency kept the same with the natural frequency of the resonator.