In this paper, the vibration energy harvesting for a bridge system under moving vehicles is studied. The vehicle model is simplified as wheel?spring?damper system, the bridge is regarded as opposite side simply?supported plate, and piezoelectric structure is composed of cantilever beam pasted with piezoelectric material and an additional mass at the end of beam. For the coupled dynamic model, first of all, differential equations of plate motion under moving load are derived from the theory of the plate vibration. Secondly, the piezoelectric coupling dynamic equation of the cantilever beam excited by the response of the bridge vibration, based on Euler Bernoulli beam theory and Kirchhoff′s first law, is obtained. Finally, the coupled differential equations of motion are solved, and the numerical simulation results are analyzed. The results show that the design of the piezoelectric structure can effectively collect the vibration energy of bridge system, and the piezoelectric device position, piezoelectric beam thickness, lumped mass, vehicle speed of piezoelectric had some effects on the energy harvesting efficiency.