In this article, a new copolymer Of L-aspartic acid and L-glutamic acid, which may be a biodegradable high molecular polymer and can be used more widely in many areas, was synthesized. The conditions of preparation, such as catalyst, reaction time, reaction temperature, the amount of catalyst, the times of adding catalyst, and the molar ratio Of L-aspartic acid to (L)-glutamic acid, were optimized. The copolymer was characterized by C-13 NMR, infrared spectroscopy, and X-ray diffractometer. The molecular weight was determined by GPC. The result indicated that production yield, purity of product, and molecular weight of product increased with amount of catalyst and molar ratio Of L-aspartic acid to L-glutamic acid increasing. The best condition of preparation was the following: reacting 2-4 h at the temperature of 180-200 degrees C. The product yield with the molecular weight 13,000.00 reached 63.2% and the purity of product was 96.33% when the copolymerization was carried out at the temperature of 200 degrees C under vacuum for 2 h. (c) 2006 Wiley Periodicals, Inc.