In this work, the ternary nanocomposites (EGSC) were prepared based on ethylene vinyl acetate copolymer (EVA), ethylene vinyl acetate copolymer grafted with acrylic acid (EVAg) and silica nanoparticles (SiO2) by melt mixing method. The effect of different content of EVAg on relative melt viscosity, thermal stability and weatherability of EGSC were investigated. The relative melt viscosity was determined by Polylab 3.1 software connected to intermixer Haake Rheomixer. The interfacial interactions of SiO2 phase and EVA phase in EGSC were evaluated by Fourier Transform Infrared Spectroscopy (FTIR) through the wavenumber shifts of characterized groups in EGSC compared to EVA, EVAg, SiO2 and Scanning Electron Microscopy images observation of EVA/SiO2 nanocomposites with and without EVAg. The tensile strength and elongation at break of EGSC were significantly enhanced when adding EVAg into EVA/SiO2 nanocomposite (ESC), especially at the ESC containing 1 wt. percent EVAg. The improvement of EVAg on thermal stability and weatherability of ESC were also discussed.