Poly(trimethylene terephthalate) (PTT)/cellulose acetate butyrate (CAB) blends were prepared by melting blending through a co-rotating twin screw extruder. The structures of PTT/CAB blends were characterized by scanning electron microscope (SEM) and Fourier transform infrared (FTIR) spectra, and the results showed that CAB phase dispersed homogeneously in the PTT matrix and there existed evident phase interface between PTT and CAB. The nonisothermal crystallization behavior was investigated by differential scanning calorimetry (DSC) and was described with modified Avrami equation of Jeziorny and Mo equation, respectively. The results indicated that the half crystallization time (t1/ 2) is much shorter, the nonisothermal crystallization kinetic rate constant (Zc) is bigger at a given cooling rate, the cooling rate [Fz(T)] is smaller at a given relative crystallinity (X t) of PTT/CAB blends than those of PTT, which proved that the addition of CAB improved the crystallization of PTT and made PTT crystallize more perfect and faster than pure PTT. In addition, thermogravimetric analysis (TGA) curves of PTT and PTT/CAB blends showed that effects of CAB content on the thermal decomposition of PTT/CAB blends were little. POLYM. ENG. SCI., 2012. (C) 2012 Society of Plastics Engineers