Aiming at the weathered red sandstone of the Leshan Giant Buddha, four organosilicon protective materials including Wacker BSOH-100, Remmers KSE-300, fluorosilane KY-60 and modified siloxane were selected for reinforcement and protection in this study. The protective effects of the above four organosilicon materials on the highly weathered red sandstone of Leshan were comprehensively evaluated through indoor reinforcement performance tests and accelerated aging tests of sunlight and rainfall. The results showed that the red sandstone of the Leshan Giant Buddha suffered from a high degree of weathering and severe weathering damage. For its weathering protection, anti-weathering reinforcement materials with strong permeability, remarkable cementation effect and good water resistance should be selected, among which KSE-300 exhibited the best protective effect. This study provides a feasible scheme for the protection of the weathered red sandstone of the Leshan Giant Buddha, and has important reference significance and popularization value for the scientific protection of the same type of large open-air sandstone cultural relics at home and abroad