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