Abstract: To improve the easily aggregated characteristics of nano-silicon dioxide,the poor bonding force between nano-silicon dioxide and the organic substrate,the epoxy resin was grafted onto the surface of nano-silicon dioxide,which was treated by the prior chain-extending reaction,taking full use of the advantages of epoxy resin such as many active groups and better hydrophobic. The best formula was obtained by the adjustment of the reactive temperature and the ratio of between epoxy resin and paraamino benzoic acid. Sedimentation experiments,water absorption measurements and infrared absorption( IR) were used to verify the modification effects,and the surface state,dispersion ability of the unmodified and modified nano-silicon dioxide were also analyzed.Resultsshow that the best modification parameters are the molar ratio is 1 ∶ 1 between epoxy resin E-44 and para-amino benzoic acid,and the perfect reactive temperature is 100 ℃. Finally, the microscopic model was created to clarify the modification mechanism.