Colloidal silica/methyltrimethoxysilane (MTMS) sol solutions were prepared in variation with the ratio of MTMS to colloidal silica. Sol solutions were prepared by sol-gel reaction. To understand their physical and chemical properties, dip coating of sol solutions was performed on the glass substrates. The state of coating films was investigated in variation with the amount of MTMS and reaction time. The contact angle and thickness of coating films increased with an increasing amount of MTMS. The surface roughness of coating films decreased with an increasing amount of MTMS. Coating films were stable until 550°C. Thermal degradation temperature of coating films decreased with an increasing amount of MTMS.