To analyze the vibration characteristic and output characteristic of the arc spiral piezoelectric energy harvester, a finite element approximation (FEA) model is proposed in this article. It is found that the FEA model can simplify the model while maintaining the accuracy of results. The modeling, simulation and measurement of the arc spiral piezoelectric energy harvester are implemented before and after the approximation. The resonant frequency, output voltage, and output power of the spiral piezoelectric energy harvester are obtained. The circular arc cantilever beam is divided into 6 ~ 16 rectangular cantilever beams with the finite element method. The resonant frequency and output performance of the arc spiral energy harvester under different degrees of FEA are analyzed. Results show that when the number of FEA sides is larger than 10, the performance of the spiral piezoelectric energy harvester has little error. A 2π spiral piezoelectric energy harvester is fabricated and measured. The test results show that the resonant frequency is 158 Hz, the theoretical resonant frequency is 153 Hz with the 10 FEA model, and the error is 3. 5% . The maximum output power is 53. 5 μW, the theoretical output power is 55. 2 μW, and the relative error is 3. 18% . The test results is in good agreement with the theoretical results.