Diethyl 2-(2-cyanoethyl)malonate was synthesized from diethyl malonate and acrylonitrile by Michael addition reaction using L-proline as catalyst. The effects of the reaction condition on the yield and the enantiomeric excess value of Diethyl 2-(2-cyanoethyl)malonate were investigated.A 74.10% yield ( the yield is higher than 67.6% in the literature which was reported.)with 79% enantiomeric excess was obtained under the optimal reaction conditions: pyridine as solvent; the dosage of diethyl malonate, 0.1mol; the mole ratio of diethyl malonate to acrylonitrile, 1:1.2; the dosage of L-proline, 0.04mol; reaction time, 48 h; and temperature, 35℃, respectively.