Abstract: Flow-induced vibration piezoelectric energy harvesting (FIVPEH) technology can convert the natural environment vibration energy into electrical energy, providing a self-powered solution for low-power micro-electro-mechanical systems. In this paper, two types of metasurface piezoelectric energy harvesters, namely bell-shaped and horn-shaped, are designed by attaching metasurface structures onto the surface of a circular cylinder bluff body. A mathematical model of the vortex-induced vibration (VIV) and galloping energy harvesting system is established. Three-dimensional CFD simulations based on the Lattice-Boltzmann method are performed to obtain the lift and drag coefficients of different bluff bodies. A wind tunnel experimental platform is built and harvester prototypes are developed to investigate the effects of the metasurface structural parameters and wind speed on the vibration response and energy harvesting performance. The results show that the metasurface has a significant regulatory effect on the aerodynamic characteristics of the bluff body. The bell-shaped structure can effectively suppress VIV, while the horn-shaped structure can induce a transition of the vibration mode from VIV to galloping, thereby significantly improving the energy harvesting efficiency. It is found that compared with the typical VIVPEH, for the attachment thickness of h = 12 mm, the maximum vibration displacement and maximum output voltage of the corresponding Bell-VIVPEH are reduced by 83.73% and 85.19%, respectively. Whereas for the horn-shaped bluff body energy harvester at the same height, the maximum vibration displacement and maximum output voltage are increased by 138.07% and 100.92%, respectively. Flow field simulations reveal that the bell-shaped structure weakens the vortex shedding process behind the bluff body, while the horn-shaped structure strengthens this process. The synergistic effect of the primary large-scale vortex and the secondary small-scale vortex is identified as the key mechanism triggering the transition from VIV to galloping. Parametric analyses further reveals that the energy harvester can increase its output power by appropriately increasing the electromechanical coupling strength. The research findings provide important theoretical guidance for designing high-efficiency piezoelectric energy harvesters.