Nano-SiO2 modified by γ-aminopropyl triethoxysilane(KH550) was used to prepare the ethylene-vinyl alcohol copolymer(EVOH)/nano-SiO2 composites through melt-compounding method and the composites were blown into films. The films were treated by UV irradiation with different treating time and intensity. Nano-SiO2 was characterized by FT-IR, TEM and SEM, the barrier properties and mechanical properties of treated and untreated composites were tested. The results showed that chemical bonds were formed between nano-SiO2 and silane coupling agent KH550, and the barrier properties, mechanical properties of the EVOH/nano-SiO2 composites were improved greatly.