The invention discloses a method for synthesizing ethanol, which comprises the following steps of: 1, preparing oxalic acid diester through coupling reaction of carbon monoxide and nitrite under the catalysis of an alumina-supported palladium catalyst; 2, pre-heating and vaporizing the oxalic acid diester and mixing with hydrogen; carrying out catalytic hydrogenation reaction on the mixed gas on a silicon dioxide-supported copper catalyst, and then cooling and distilling the reaction product to obtain ethanol. The preparation method of the invention realizes over 80% of selectivity and high yield of ethanol, and the gas used in synthesis process can be completely converted through circulation, thereby establishing a good foundation for research on the industry of synthesizing ethanol frombiomass.