Abstract: <SPAN lang=EN-US>Silica powder was prepared from sodium silicate and hydrochloric acid,and the surface of product was modified by surfactant.Firstly the modifiers were selected by sifting.Then,three statistical methods (range analysis,variance analysis,and multiple regression analysis) were applied in data analysis of orthogonal experiments by using mathematical software SPSS13.0.Influences of four factors,such as modifying time,temperaure,dosage of modifier,and dosage of isopropanol on product activation index,were discussed and the accordant results were obtained,namely,the optimal process conditions were followed by modification temperature of <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" /><st1:chmetcnv w:st="on" UnitName="℃" SourceValue="85" HasSpace="True" Negative="False" NumberType="1" TCSC="0">85 <SPAN lang=EN-US style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman""><SPAN lang=EN-US>℃</SPAN></SPAN></st1:chmetcnv>,modification time of 120 min,dosage of modifier A-151 of 20% and dosage of isopropanol of 15 mL.Moreover,under these conditions,the activation index of modified product was 35%,which showed fine hydrophobic property.</SPAN><BR>