Abstract: Ascries of silica gel packing materials are prepared by bonding organic silane on the silica gel surface with different concentrations of γ-glycidoxypropyltrimethoxy silane water solutions. The graft degree of the bonded phase on these silica gelssurface arc determined by using three methods——Thermal Analysis, ElementAnalysis, and absorption in solution. The results indicate that TAis a suitable method for characterizing the graft degree of the bonded phase of these modified silica gels.