The harmonic oscillator of three-component acceleration seismic geophone based on photoelastic effect is designed by the methods of inertia force perpendicular to the harmonic oscillator and differential detection technology. In terms of dual M-Z interferometer of three-component acceleration seismic geophone, equal division of optical power and single-mode transmission of light are the bases of correct acceleration detection. The structure of M-Z interferometer is introduced. The optical field transmission of dual M-Z interferometer in three-component acceleration seismic geophone is simulated by the waveguide optics simulation software OptiBPM v9.0, and the optical field transmission graph of dual M-Z interferometer is obtained. The simulation result shows that when the light emitted from the laser passes through the dual M-Z interferometer, the optical field peak values of 1/4 branch waveguides all achieve 0.52, and the splitting ratio is 1:1:1:1. The equal division of optical power is realized, and the harmonic oscillator designed meets the demand of proper acceleration detection of three-component acceleration seismic geophone.