Abstract: Flow-induced vibration contains considerable energy, which can be converted into electrical energy through energy harvesting. To improve the energy conversion efficiency in low-speed flow fields, the influence of bluff body and the ratio between width and thickness (W/T) on flow-induced vibration energy harvesting performance under different cross-sections was investigated experimentally, and the wake characteristics were analyzed by computational fluid dynamics (computational fluid dynamic, CFD) simulation. The energy harvesting device consists of a piezoelectric cantilever beam and a bluff body with various cross-sections. Firstly, according to the flow-induced vibration theory, a wind tunnel experimental platform for flow-induced vibration energy harvesting was built. The section of the bluff body is set to be rectangular, triangular and D-shaped, and the ratio of width to thickness is set to 1, 1.3, 1.8 and 2.5, respectively. The influence of W/T of the bluff body on the flow-induced vibration energy harvesting was analyzed experimentally. Finally, the insight mechanism of the experimental results is revealed through the computational fluid dynamics simulation. If the section of bluff body is rectangular, increasing the value of W/T will significantly increase the maximum output voltage. However, if the section of bluff body is triangular and D-shape, the vortex-induced vibration (VIV) will occur in the low flow speed region with the increase of W/T, which could improve the energy harvesting effect for low wind speed. The experimental results can be revealed by the related CFD simulation. As the CFD simulation at U = 3 m/s shows, with the increase of W/T, the configuration will lead to more powerful vortex streets, which can significantly enhance the energy harvesting performance of flow-induced vibration. This study can provide a theoretical and experimental basis for the structure optimization of flow-induced vibration energy harvesters and improve the energy conversion efficiency for the low-speed wind.