Nanosilica was midified by coupling agents. alcohols and dodecanoic acid, the effects of different modifiers and methods on hydrophobic stability of silica were studied, and groups on the surface of Nanosilica were characterized by FTIR. UV spectrum TG and XPS. Measurement of viscosity and precipitation experiment indicated that hydrophobic stability of silica was greatly improved by surface modification. Dodecanol and dodecanoic acid were best modifiers and the high pressure method was more effective than...