The synthesis of diethyl carbonate starting from ethanol and carbon dioxide was studied. The ZrO2 obtained by precipitation method was used as the catalyst. When the 3A molecular sieve was added as the co-catalyst, the DEC yield was effectively improved about 2.5-fold. The optimal mass ratio of ZrO2 and 3A molecular sieve was 5:2. In addition, the catalyst was characterized by the means of XRD, BET, TEM, NH3-TPD and CO2-TPD. It was indicated that the crystal type, acidic-basic properties of ZrO2, and the pore size of molecular sieve might be the main factors impacting the catalytic activities. By the optimization of the catalyst and the reaction operating conditions, when CO2 and ethanol were charged with the molar ratio of 514/225 mmol, the yield of DEC produced at 150 A degrees C and 7.0 MPa was 0.384 mmol in 2 h with the selectivity of 85.1 %.