Abstract: The oxidative carbonylation of methanol and ethanol to asymmetric methyl ethyl carbonate (MEC)catalyzed by CuCl coordinated with Schiff base ligands has been studied. A thermodynamic analysis of this process was carried out to discuss the possibility. The equilibrium constant of the main reaction at 298.2 K is 2.39×1080, so the possibility of this reaction is high. The effects of volume ratio of methanol to ethanol, molar ratio of 1,10-phenanthroline(phen)to N-methylimidazole(NMI), temperature, pressure on the conversion of methanol, ethanol and the yield of methyl ethyl carbonate have been investigated. CuCl/phen/NMI catalytic system was found to be active in the ox-idative carbonylation of methanol and ethanol to asymmetric methyl ethyl carbonate. When the reaction was carried out for 2 h at 393 K and 2.4 MPa (CO+O2) in the MeOH/EtOH system, with CuCl 0.20 molL-1, n(CuCl)∶n(phen)∶n(NMI) =1∶1.25∶1.25, and the ratio of vMeOH/vEtOH =2∶8, the conversion of methanol and ethanol are 44.3% and 22.3%, 17 and 9 times higher than that of CuCl system. The yield of MEC was 10.4%, which is increased about 74 times. The mechanism of synthesis of asymmetric carbonate was also discussed in detail.