A fiber-optic phase modulator(FOPM) is designed and fabricated in this paper,which is based on the electrostatic-driven micromirror by MEMS technology.The electrostatic actuator using the vertical comb driver is designed to drive the Si-micromirror in out-of-plane piston motion to modulate the incident light.The MEMS micromirror is coulpled with the fiber collimator to implement the FOPM.The scheme avoids the stretching or changing refractive index of the fiber and takes advantages of batch fabrication and low cost.The MEMS-FOPM is(achieved successfully by MEMS process and the fiber-optic Michelson interferometer is realized using the fabricated FOPM.Its static characteristics are measured by the fiber-optic Michelson interferometer with ASE source.Its dynamic response was measured by a Michelson interferometer.The results show the FOPM can realize 2π phase modulation with 1 550 nm wavelength at 50 V dc driving voltage.Its dynamic displacement at its mechanical resonant frequency of 7.15 kHz is 6.8 μm under 12.5 V ac driving voltage with 12.5 V dc bias voltage,so it can realize multiple 2π sinusoidal phase modulations.