It is proposed a new structure of the retro-reflection plane material, in which the gradient index micro-spheres substitute for the traditional homogeneous glass spheres with high refractive index. Using the theoretical calculations of the light tracking by quadrivalence Runger-Kutta method, the technical condition of the retro-reflecting plane material of GRIN micro-sphere is obtained. The result shows that on this condition the former high demand for refractive index of medium can be highly reduced, and the function of retro-refraction of the material is improved greatly.