A method for preparing N,N′-bis(2-cyanoethyl)-1,2-ethylenediamine involves using strongly acidic cation exchange resin as a catalyst for synthesis, and is advantageous for not only eliminating the need of distillation for purification and thereby reducing reaction time, but also improving the yield of N,N′-bis(2-cyanoethyl)-1,2-ethylenediamine to 97.70-98.08%; and the method benefits simplified process and reduced costs and helps to save water significantly, thereby minimizing environmental pollution.