Abstract: In this paper, nano-porous silica films are prepared via Sol-Gel process with base, acid and base/acid two-step catalysis. TEM and Particle Size Analyzer are used to characterize the properties of the microstructure and particles size distribution of the sol. FE-SEM, AFM and Spectroscopic Ellipsometer are used to characterize the surface microstructure and optical properties of the film. Structure controlling by changing the catalysis conditions during Sol-Gel process is investigated, and the stability of the sol during long-term storage is studied.