Nano-CeO2 was prepared through the calcination of Ce(OH)3 precursor in different atmospheres (H2, Ar, air, O2), which was prepared by a hydrothermal method, and then used as catalysts in the direct synthesis of dimethyl carbonate (DMC) from methanol and CO2. The results indicated that the catalyst calcined in O2 (CeO2-O2) showed an optimum catalytic performance, and the yield of DMC reached to 1.304mmol/mmolcat. In addition, reaction temperature and weight of catalyst were optimized. Based on characterizations of the catalysts, the ratio of Ce(IV)/Ce(III) and Lewis acid-base property of nano-CeO2 catalyst could be adjusted through different calcination atmosphere treatment. It was determined that the higher activity of CeO2-O2 catalyst is mainly attributed to its higher ratio of Ce(IV)/Ce(III) as well as abundant and moderate intensity Lewis acid base sites.