The optimization of location and size of the piezoelectric patch on the cantilever for vibration energy harvesting are studied in this work. Firstly, the strain equation and the opencircuit voltage and energy equation are analyzed and deduced integrally.Secondly, the novel optimization methods for location and size of the piezoelectric patch are proposed. Lastly, the calculative optimization location and size of the patch for the first and second modes are achieved by executing the proposed optimization method, and the further simulation analysis is carried out using the abaqus software. The result of theoretical calculation and simulation analysis are basically the same: the optimal location of the patch is at the root of cantilever under the first mode and at the middle of cantilever under the second mode, and the optimal size is about half the length of cantilever under both first and second modes. And the result shows that the optimization methods proposed in this paper are correct and effective.