Polysuccinimide (PSI) was first synthesized via thermal polycondensation reaction using maleic anhydride and urea as the starting materials. Then, polyaspartic acid–glutamic acid (PASP–GLU) grafted copolymers were prepared from PSI and GLU. The structure of PASP–GLU was characterized by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. The molecular weight was measured by gel permeation chromatography, and the crystallinity was analyzed by X-ray diffraction spectra. The effects of grafting ratio on the builder performances were systematically studied, as well as on the thermal property and biodegradability. It is demonstrated that as the grafting ratio of GLU increases, the thermal stability and biodegradability decrease a little, but still maintain in high level. Most importantly, the incorporation of GLU into side chains significantly improves the builder performance of PASP–GLU. The maximum values for calcium ion chelating power, dispersion power of CaCO3, and alkali-buffer ability reach 233.2 mg, 108.9 mg, and 1.70 mL, respectively, at the highest grafting ratio, in which the dispersion power of CaCO3 and alkali-buffer ability are even better than that of sodium tripolyphosphate. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40282.