On the basis of Micro-electro-mechanical System(MEMS), a broadband electrochemical seismometer was developed. The structure parameters related to the seismometer were analyzed and a developing scheme based on MEMS technology was presented to extend the frequency band of the seismometer to a wider range. The effects of the lengths of insulating spacers and the pore widths in cathodes on the seismometer property were discussed by numerical simulation and the optimized structure parameters were obtained. Then, according to simulation results, the Su-8 series photoresist and a silicon wafer were applied to fabrication of spacers and electrodes with optimized sizes. These devices were packaged via a physical fastening method to avoid the leakage of electrolyte. Finally, the device characteristics were measured through frequency response test on a horizontal vibration platform and a micro seismic monitoring experiment was performed on the bedrock. Test results without frequency compensation demonstrate that the frequency band of the device packaged with spacers with thickness of 200 μm and cathodes with wide pores of 20 μm has reached 3-90 Hz, the fade degree at 60 S is less than 30 dB, and the seismometer's dynamic range is no less than 130 dB. This improved seismometer may function as a detecting device covering a wide frequency range in the marine oil exploration.