A new bistable energy harvester with a shaped hole in the cantilever beam substrate is designed to address the problem of high resonant frequency and rapid decrease in output voltage when deviating from the resonant frequency of the conventional linear piezoelectric cantilever beam energy harvester. The theoretical model of this energy harvester is established, an experimental prototype is fabricated, and the effect of magnetic spacing on the output voltage and operating band of the energy harvester under different external sinusoidal excitation frequencies is studied. The results show that the bistable effect of the bistable energy harvester with a shaped hole structure is enhanced and then weakened as the pole pair spacing decreases. From this, it is determined that the optimal pole pair spacing is 12 mm, the resonant frequency is 18 Hz, the maximum output root-mean-square (RMS) voltage reaches 12.01 V, the effective operating frequency of the harvester ranges from 15.5 Hz to 22.5 Hz, and the operating bandwidth reaches 7 Hz. The bistable energy harvester with shaped hole has a wider acquisition band and a higher output voltage response under the low-frequency vibration environments.