On-line monitoring of transformer vibration signals is an important method to detect the operating status of transformers. The power supply mode of the vibration sensors restricts the application of vibration detection methods. To access the power supply for the vibration sensor,a transformer vibration energy harvesting device based on piezoelectric material is designed,which uses the collected vibration energy to supply the vibration sensor. Firstly,according to the vibration characteristics of transformer,the output voltage and output power models of the three-cantilever piezoelectric energy extraction structure are established using the multi-modal energy harvesting method. Then,the relationship between the output power of the energy harvesting device and the external excitation frequency is analyzed by Comsol Multiphysics simulation. Finally,the transformer vibration energy harvesting experiment platform is built,and the actual output power of the piezoelectric energy collecting device is measured to be 11.547 μW. Using the vibration energy harvesting device could supply power to the oscillation sensor,which can ensure the power supply of the online monitoring equipment and reduce the influence of the external power supply on the safe and stable equipment operation.