Focusing on the demand for collecting the wasted mechanical energy from nature or human production activities in the current period, the design and development of piezoelectric energy harvester with higher electromechanical conversion performance of great significance. To solve this issue, we designed a piezoelectric energy harvester based on the combined action of an annular hollow mass and springs. When vibrating, the force exerted by the mass is released at the three equal points on the surface of the brass substrate through 3 parallel springs. This concentrated release of energy through the spring amplification effect facilitates large deformation of the piezoelectric ceramic sheet, resulting in more charge output. The results show that such an energy harvester based on the PZT-5H ceramic can exhibit an ultra-high output power of 23.69 mW at a low frequency of 70 Hz under the joint action of only a 14 g mass and three springs of 0.3 mm wire diameter, 2 mm outer diameter and 5 mm length. More importantly, to match the vibration frequency of the actual environment, we also proposed that energy harvesters can be designed by selecting spring wire diameter and the weight of mass. The energy harvester designed in this work is expected to capture energy from low-frequency natural environments and exhibit outstanding output performance, which can provide guidelines for future efforts in this direction.