Abstract: Based on single-factor experiments，preparation technology of ultrafine silica with silicon tetrachloride and sodium silicate as raw materials was optimized by response surface and mathematic model was established.Influences of the interaction of various factors，such as mass fraction of sodium silicate，mass fraction of additive，and reaction temperature on DBP absorption value of silica were investigated.The optimum conditions were confirmed as follows: the mass fraction of sodium silicate was 8.6%，the mass fraction of additive was 2.7%，and the reaction temperature was 76 ℃.The DBP absorption value of silica was 2.806 7 under the optimum conditions，with the error of 0.005 6 compared with the predict value of 2.801 1.It revealed that the model had better fitting degree，and could reflect the influence of various experimental factors on DBP absorption value.

Key words: silicon tetrachloride, response surface, ultrafine silica