Nanocomposites of ethylene-vinyl acetate copolymer (EVA)/nanosilica in presence of EVA-graft-maleic anhydride (EVAgMA) were prepared via sol-gel method by using tetraethylorthosilicate (TEOS) introducted into the EVA and EVAgMA solution. The nanocomposites were obtained after evaporation of solvents. Fourier Transform Infrared spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM), thermogravimetric analysis (TGA) were used to characterized the nanocomposites and their mechanical properties were also tested. The FTIR spectra of the nanocomposites and TGA diagrams of the nanocomposites showed that silica has been formed, and FESEM micrographs of the nanocomposites revealed the nanoscale of silica particles dispersed in the nanocomposites. The FTIR spectra of the nanocomposites also demonstrated the shifts of Si-O stretching vibration in the nanocomposites in comparison with pure silica. This suggests the formation of hydrogen bonding between silanol groups at surface of silica nanoparticles and carbonyl groups of EVA copolymer. In the presence of EVAgMA, the sp-onger interaction and adhesion between silica and EVA has been proved by the higher shifts of Si-O vibration bands in FTIR of the nanocomposites. The nanoscale of silica particles and the interaction between them and EVA matrix were reasons for the enhancement of mechanical properties and thermal stability of the EVA copolymer, and EVAgAM can further enhance these properties of EVA/silica nanocomposites.