This paper presents an electromagnetic vibration energy harvester utilizing 3D MEMS coils and multi-mode structure to improve the output power and broaden the frequency band. We fabricated and assembled the prototype, with a pair of 3D coils fabricated by lithography, silicon etching, silicon direct bonding and copper electroplating, et al., which are compatible with CMOS processes. The numerical simulation was conducted to analysis the vibration modes of the spring-mass system, which revealed the multi-mode mechanism of serpentine springs. We also tested the output power-frequency curves for different load and excitation acceleration to investigate the optimal load resistance and the influence of excitation. The test results showed that the proposed prototype can generate 1.2μW power under 992Hz for 1g acceleration with a half-power bandwidth of 65Hz, which are higher than some recent published data, proving the superiority of proposed structure.