In this paper, a novel energy conversion method based on hydrogel material for self-powered sensor system applications is proposed, which can harvest energy from environment vibrations and supply power to sensors without any external power source. In this approach, hemispherical hydrogel arrays are positioned between two parallel-arranged conductive plates. The deformation of hydrogel arrays caused by ambient vibrations will result in non-equilibrium charge distribution in the conductive plates. The charge redistribution leads to electrons transfer, thereby converting mechanical vibration energy into electricity. Based on this energy conversion principle, a hydrogel-based energy harvester is fabricated and experimentally characterized. The fabricated device exhibits a superwide working bandwidth (0–80Hz) and high reliability in power generation. Moreover, favorable adaptability of the tilt angle during installation is achieved. In the feasibility experiment, an LCD screen is operated to verify the potential of the hydrogel-based energy conversion method to self-powered sensor applications under vibration environment. Finally, a visualized self-powered force sensor is also demonstrated with the fabricated hydrogel-based energy harvester, which proves its great potential in various application fields.