The piezoelectric energy harvesters can convert the vibration energy into the electric energy and supply power for the low-power electronic equipment. In order to broaden the effective frequency band width of the piezoelectric energy harvester and reduce the resonant frequency of the system, a piezoelectric energy harvester with additional liguid mass is proposed in this paper. Guided by the piezoelectric effect, the mechanical model and electromechanical coupling model of piezoelectric energy harvester are established, and the dynamic characteristics of piezoelectric energy harvester with additional liquid mass are analyzed, and the study is carried out based on the theoretical model, simulation analysis and experimental verification. By making a prototype and building a vibration experiment platform, the energy harvesting characteristics of piezoelectric energy harvester are tested experimentally, The experimental results show that compared with the traditional cantilever piezoelectric energy harvester, the resonant freguency of the piezoeleetric energy harvester with five modes of the structure is signilicantly reduced, and the output voltage is increased. The AC-DC rectifier filter circuit is used to rectify and filter the electricity generated by the piezoelectric energy harvester, and the availability of the electric energy generated by the piezoelectric energy harvester is verified