Homodyne interferometry based on nonlinear GaAs crystal for micro-vibration measurement is investigated by conducting an experiment. In the interferometer that with 532 nm laser, signal beam is modulated by a vibrating mirror and interfers with reference beam on the surface of GaAs crystal. The interferometric signal produces photo-induced current that relates to vibration amplitude when vibration frequency is beyond cut-off frequency of GaAs crystal. Influences of spatial frequency of interferometric fringes and electrode space of GaAs crystal on the photo-induced current of the GaAs crystal are studied and the optimum parameters are obtained. Experimental results are compared with those from a commercial vibration measurement instrument and coincided well.