Glass materials have been applied in various industrial fields. Research on improvement of mechanical properties has consistently been performed due to this material’s intrinsically vulnerable characteristics. Surface modification is considered as the promising method to supplement the weakness; especially, ceramics are thought of as appropriate materials for film materials because of their outstanding mechanical properties and their chemical stability. However, unfortunately, the optical transmittance of ceramic materials is poor, and can rather restrict this material’s utilization in glass. In this regard, the optical transmittance mechanism of vacuum kinetic sprayed Al_{2}O_{3} film was investigated. To control and analyze the film’s optical property, the gas flow rate, as a main process variable, was controlled; then, post heat-treatment was performed. Consequently, the film’s optical property was determined by three microstructural factors. That is, crystallite size, defects (including lattice distortion), and amorphous phase, generated during particle deposition, were found to strongly affect the transmittance.