A micro electrostatic seismic power generator based on a droplet was proposed for harvesting the seismic energy in low frequency to improve its low frequency response and impact resistance abilities. The generator structure was based on the charge transfer between the differential capacitors inducted by the movement of the micro droplet in the electric field of an electret. According to the electret model, the charge distribution on the differential capacitors was derived. Combined with the assumption of forced sinusoidal vibration of the micro droplet, a mathematic model of the micro power generator was established. The COMSOL Multiphysics was employed to simulate the micro droplet movement and charge distribution, then the voltage-frequency characteristics were obtained. A prototype of the electret and micro-droplet-based micro seismic power generator was developed and tested. Its resonant-frequency is 3 Hz, the output power is about 0.73 μW on 1 MΩ resistance when the vibration acceleration is 3 g under a resonant frequency. It can scavenge the energies from low-frequency external vibrations.