Abstract: The preparation of sitagliptin related substances by the aza-Michael addition reaction of dime-thyl-maleate or maleic acid to sitagliptin is crucial to assist in research of the risk control of sitagliptin drug impurities：①Using sitagliptin and dimethyl fumarate as raw materials, 1,8-Diazabicyclo（5.4.0）undec-7-ene (DBU) as a catalyst, stirring at 25?C for 6 hours under N2 protection, separation and purifi-cation by Ethyl Acetate - HCl - H2O crystallization system, 76 % yield of the sitagliptin impurity I, 99% purity by HPLC; ②Maleic acid as raw material, stirring at room temperature for 2 hours with K2CO3, to prepare sitagliptin impurity II by one-step method, up to 98% yield. The two kinds of sitagliptin impurities have been synthesized with good yield and high purity, and has the advantages of short route, low energy consumption, low production cost and simple operation for industrial production.