Pyramid is a typical kind of cone structure. When the light passes through the “pyramid” array,it is equivalent to pass through a thin film with a graded refractive index,and the Fresnel reflection at the interface is greatly weakened. The surface reflection characteristics of the sub-wavelength structure composed of three materials(Si,SiO2,Ge) were simulated with DiffractMOD in Rsoft. The results show that the sub-wavelength structure composed of SiO2 has good optical anti-reflection characteristics.