Abstract: Silicone flame retardants were synthesized through co-hydrolysis condensation reaction by using methoxysilanes with methyl and phenyl groups as the raw materials.The synthesis process was studied and optimized through orthogonal analysis of the reaction temperature, reaction time, catalyst quantity, and blocking time.The results indicated high thermal stability of the silicone.The mass loss was less than 39% at 800℃ in nitrogen atmosphere.Further more, the study showed that higher thermal stability of the silicone made it an effective flame retardant for polycarbonate.The oxygen index of polycarbonate was increased from 26.0 to 34.0 when 5% (mass) silicone made by this optimized conditions was added.