An L type broadband piezoelectric energy harvesting device was proposed in this paper, and the finite element model of L-type piezoelectric vibrator is established and simulated. It shows that the voltage corresponding to the first and third order resonant frequency is 0.06 V and 0.183 V, respectively, although higher than that of the ordinary piezoelectric vibrator, the voltage of the first mode and third mode for the piezoelectric vibrator is not close, which has little effect to broaden the bandwidth. Consequently, the simulation model for multi-cantilever piezoelectric vibrator was established, and its structural sizes were optimized, and it was obtained very close to first and third order resonant voltage, the bandwidth of the vibrator was broadened to 12.5 Hz. The multi-cantilever piezoelectric vibrator can be applied in a variety of devices for the collection of mechanical energy, and to provide a research foundation for the development of intelligent structures with self-sufficiency.