With the help of differential scanning calorimeter (DSC), the basic thermal behaviors, nonisothermal crystallization kinetics, and subsequent melting behaviors of poly(butylene succinate) (PBS) and its copolyester (PBSTMA) modified with trimellitic imide units were investigated in this paper. The DSC thermograms of PBS and PBSTMA showed that the crystallization behaviors of PBS were affected seriously because of the addition of a small quantity of trimellitic imide units. The nonisothermal crystallization processes of them were represented by the Avrami equation modified by Jeziorny and the method developed by Ozawa. After that, the conception of "crystallization rate coefficient (CRC)" introduced by Khanna was employed. The values of CRC for PBS and PBSTMA are 174.6 and 88.2 h(-1), respectively. At the end of this paper, the melting behaviors of PBS and PBSTMA after being cooled from 130 to 30 degrees C at different cooling rate were studied in detail. (c) 2006 Wiley Periodicals, Inc.