In this study, silica nanoparticles or nanosilicas were prepared through a sol-gel process. Then, 3-aminopropyltrietoxy silan (APTES) compounds were hydrolyzed in ethanol solvent and added the above silica nanoparticles into the hydrolyzed APTES solution. The organic chains in APTES grafted to surface of nanosilica were detected by Fourier Transform Infrared (FTIR). Surface characteristics (including specific surface area, pore volume and pore size) of nanosilica and modified nanosilica were measured by nitrogen adsorption and desorption. The grafting yield of APTES for monolayer formation on the nanoparticles surface was determined by Thermogravimetric Analysis (TGA) technique. Finally, the morphology of unmodifed and modified nanosilica was characterized by Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM). It can be seen that agglomerated particle size in modified nanosilica decrease in comparison with unmodified nanosilica. The above results showed that surface treatment of nanosilica with APTES is successfull.