A distributed fiber vibration sensor based on 3×3 Michelson interferometer is proposed, and a 3×3 interferometer is used to build the structure of a phase sensitive optical time domain reflectometer (φ-OTDR) based on homodyne coherent detection. With transfer matrix phase demodulation algorithm and through the basic parameters of the 3×3 interferometer transmission matrix, the corresponding relationship between differential phase and interferometer output light intensity is established. The simple and efficient software computing programs are used to demodulate the differential phase of Rayleigh scattering light in optical fiber, so as to realize the optical fiber distributed disturbance detection. The system is also used to detect the vibration along the fiber, and the experimental results show that the sensing system can accurately locate for the vibration and restore the frequencies of audio and radio frequency drivers, of which the effective sensing distance is 10 km.