Abstract: Composites of polyethylene glycol terephthalate (PET) and nano magnesium oxide（nano-MgO）were prepared by melt blending. The ultravioletshielding property of the composites was tested by ultravioletvisible absorption spectra. It is shown that when the content of nanoMgO was 1 %，the notch impact strength of the composite was 15 % higher than neat PET. When the nanoMgO content was 2 %, the tensile strength of the composite was 8 % higher than neat PET. SEM showed that the nanoMgO was welldispersed in the composites. When the content of nanoMgO was 2 %，the half width of the crystallization peak of the composite was 7.7 ℃, which was 15 % lower than neat PET. The import of nanoMgO could improve the melting point of PET. When the content of nanoMgO was 2 %，the half width of the melting point of the composite was 252.4 ℃, which was 4.1 ℃ higher than neat PET. When the content of nanoMgO was 3 %，the cutoff wavelength of ultravioletshielding property of the composite was 300 nm, which was 11 % higher than neat PET.

Key words: poly(ethylene terephthalate), nano magnesium oxide, mechanical property, crystallization property, ultraviolet-shielding