A wireless bridge health monitoring system is introduced. Arming at the difficulty of changing battery, a piezoelectric energy harvesting circuit is presented. This self-powered structure use multi-cantilever to broaden the resonance frequency band of the piezoelectric vibrator. Then, we use standard circuit and LTC4071 to transfer the energy to the lithium battery. The experimental results show that the piezoelectric energy harvesting circuit can support the normal operation of the bridge health monitoring.