Monodispersed silica spheres have attracted much attention because of their widely applications in the areas of catalysis, adsorption, chromatography packing materials and advanced ceramics. This paper focused on its application as a packing material of function coatings for space applications. Nanosized monodispersed silica spheres can be fabricated by Stöber method. However, microsized monodispersed silica spheres are not easy obtained. In this paper monodispersed silica spheres with the size between 200nm to 2000nm were fabricated by hydrolysis of tetraethoxy silane (TEOS) in isopropyl alcohol solvent and using ammonia as catalyst through multi-step growth method. The influence of silica seed number density and TEOS concentration on monodispersity and size of silica sphere were studied. The result shows that monodispersed silica spheres could be obtained through control the concentration of TEOS and the silica seed number density during every growth step. The diameter of monodispersed silica spheres increased with the steps of growth.