Stearic acid methyl diethanolamine ester was synthesized from stearic acid and N-methyl diethanolamine, and then the intermediate was quaternized by γ-chloropropyl methyl dimethoxysilane to get the product siloxane quaternary ammonium salt containing ester group in this study. The effect of molar ratios of raw materials, reaction temperature, reaction time and catalyst dosage on the conversion of stearic acid were investigated by the orthogonal experiment. The optimal reaction conditions for the esterification were found to be 180℃ for 6h with hypophosphorous acid as ascatalyst at 1.6：1.0 molar ratio.The maximum yield of product was 56.42% in dimethyl sulfoxide. The intermediate and product were characterized by FTIR. The surface chemical properties were investigated at 298 K. The result show that the cmc is 0.197g/L, the γcmc is 24.25 mN/m, surface tension is 19.65mN/m and the softening performance of the sample is superior to general commercial products.