A new class of vibration energy harvester was introduced based on piezoelectric effect, which is composed of a buckling unimorph PZT beam, a mass and a nonlinear spring. Based on the Euler-Bernoulli beam model, the nonlinear governing equations were constructed for the energy harvester using Hamilton′s principle. First, the natural frequency was computed and discussed with the change of structural parameters. Then, the method of multiple scales was utilized to perturbation analysis. And the amplitudefrequency characteristics were discussed based on numerical simulation. The nonlinear jumping phenomenon is found for the vibration energy harvester. Finally, the voltage effect of the energy harvester was discussed between the output voltage and the external excitations.