An amorphous silica film has been coated on a fused silica glass and KH2PO4 [KDP] crystal by using the photo oxidization of Dimethy-siloxane silicone [DMSS] oil by using a xenon [Xe2] excimer lamp at room temperature. The DMSS oil [-O-Si[CH3]2-O-]n was spin-coated on a fused silica glass to make a thin film, and the Xe2 lamp light was vertically irradiated in the presence of oxygen. Thus, the organic oil was changed into inorganic glass. In order to investigate the photochemical reaction process, the fluorescence intensity was measured by spectrometer at actual time and the new method to form a transparent, photo-oxidized thin film efficiently has been established. The interferometer analysis was conducted to investigate the strain of the coating samples. It became clear that the no strain were caused by vitrification of the silicone oil on the fused silica galass with Xe2 lamp irradiation.