The invention discloses a method for preparing N-ethoxy oxalyl alanine ethyl ester. The method comprises the following steps: heating and dissolving alanine, oxalic acid and alcohol, and then adding a catalyst, a water-carrying agent benzene and diethyl oxalate, wherein the catalyst is a mixture of sulfuric acid and urea in a molar ratio of 1: (1-3); heating the obtained mixture to 60-100 DEG C; carrying out reflux rectification reaction for 10-150 hours, wherein in the process of reaction, the water produced in the process of reaction is timely evaporated by using the water-carrying agent benzene; and after the reaction is finished, carrying out after-treatment so as to obtain a target product, namely, the N-ethoxy oxalyl-alanine ethyl ester. Compared with the prior art, the method disclosed by the invention has the following advantages that: the catalyst is the mixture of sulfuric acid and urea, therefore, the catalyst has acidity catalytic activity and contains ammonium salt cations, and the ammonium salt cations can be adsorbed on the surface of metal, thereby reducing the corrosion of the catalyst on equipment; and meanwhile, the catalytic efficiency is high, the reaction yield is high, and the side reaction is less.