Polyaspartic acid (PASP) is suitable for the inhibition of scale deposition from water. To enhance its inhibition efficiency, PASP was modified by reacting aspartic acid (Asp) with glutamic acid (Glu) to provide Asp-Glu copolymer under microwave irradiation. The influence of reaction parameters on conversion, molecular weight and inhibition of CaCO3 precipitation. was investigated Infra-red. (IR), H-1 nuclear magnetic resonance (H-1 NMR) and C-13 nuclear magnetic resonance (C-13 NMR) spectroscopies were used to characterize the copolymer. The results show that copolymerization of aspartic acid and glutamic acid is catalyzed by a small amount of phosphorous acid (H3PO4) in solvent, the product conversion is 98.05% under the following conditions: the molar ratio of glutamic acid to reactant [Glu/(Asp+Glu)] is 0.3 and that of catalyst (Cat) to reactant [Cat/(Glu+Asp)] is 0.05 (0.65ml H3PO4), the volume of solvent dimethylformamide is 16ml, the microwave power used is 720W and the reaction for 3 min. The weight average molecular weight of copolymer synthesized under these conditions is 2709 and the inhibition rate for CaCO3 is 97.75%.