A silicon-halogen synergistic flame retardant plasticizer benzyl trichloroethyl silicate was synthesized by using silicon tetrachloride, benzyl alcohol and ethylene oxide as raw materials. The effect of reaction time, temperature and amount ratio of substance on product yield was discussed．The optimal conditions for preparation r were selected as follows: n(silicon tetrachloride):n(benzyl alcohol) was 1: 1; n(silicon tetrachloride):n(ethylene oxide) was 1: 3.2; reaction time was 2h at 30℃ and the percentage of product yield could reach 98%. The molecular structures of benzyl trichloroethyl silicate and its related performance measurement were determined by means of FTIR，1H NMR and LOI technique.