In order to reduce the resonant frequency, achieve multi-directional collection, and improve the output performance, a 4π arc spiral piezoelectric energy harvester is proposed. The device performance was improved by analyzing the relationship between device size and output performance. The optimized model was simulated in COMSOL to analyze vibration displacement, stress, and resonant frequency. Compared with the 2π arc spiral piezoelectric energy harvester, the 4π arc spiral piezoelectric energy harvester has a lower resonant frequency and a higher output. The 4π arc spiral piezoelectric energy harvester has a resonant frequency of 48 Hz, an output voltage of 12.3 V, and an output power of 400 μW.