This paper presents a factional model for broadband piezoelectric energy harvesting systems. Piezoelectric materials pay a significant role in harvesting ambient vibration energy. Due to their inherent characteristics and electromechanical interaction effect, piezoelectric energy harvesting exhibits the hysteresis characteristic under sweeping environmental vibration. Fractional order model of piezoelectric energy harvesting could capture the hysteresis characteristics. Simulation and experimental results show that fractional model of piezoelectric energy harvesting is more effective in describing the system dynamic.Copyright © 2015 by ASME