In order to expand the low reflective properties of silicon solar cells in a perfect frequency range, a kind of optical microstructures composed of period arranged spherical silica particle was designed. The excellent anti-reflective property of optical micro/nano-structure was used to expand the ultra-low reflective property of silicon solar cells. First, the scattering property of a single spherical silica particle was studied using Mie scattering theory. Then, the reflective property of periodic two-dimensional optical micro-structures composed of multiple particles was analyzed by simulation software "MEEP". The results of the simulation demonstrate that when the radius, spacing and periodic number of spherical particles are reasonably selected, the ultra-low reflection will occur in a perfect frequency range.