The invention belongs to the synthesis of organic carbonates and relates to a technology of synthesizing diethyl carbonate by a urea alcoholysis method. The technology comprises the steps of: adding anhydrous ethyl alcohol, ethyl carbamate and a catalyst into a high pressure reaction kettle, wherein the mole ratio of the anhydrous ethyl alcohol to the ethyl carbamate is 2 to 25, and the catalyst is combined metal oxide, and accounts for 0.5 to 10 percent of the whole system by mass percent; raising the temperature to 150 to 200 DEG C by stirring so as to carry out reaction for 1 to 15 hours; and taking out the reaction liquid after the reaction, and realizing the separation of the catalyst and the reaction liquid by simple filtration. The combined metal oxide is prepared by 2 to 3 metal oxide precursors among Li, Na, K, Ca, Mg, Ba, Sr, Al, Sn, Pb, La, Ti, W, Zr, Fe, Co, Ni, Cu and Zn through thermal decomposition method or coprecipitation method. The preparation method of the technology is simple, the catalyst activity is high, the stability is good, and the separation and recycling are easy.