Poly(trimethyleneterephthalate)(PTT)/styrene-ethylene-buthylene-styrene(SEBS)composites were prepared by melt compounding.Polarizing opticalmicroscopy was used to observe the spherulitic morphology and the crystalstructure of PTT and PTT/SEBS composites.Scanning electron microscopy was used to determine the dispersion and the compatibility of fracture surfaces of PTT and SEBS.The curves of thermalgravimetric analysis illustrated that the thermo stability decreased with increasing SEBS content.Differentialscanning calorimetry was used to investigate the crystallization behavior;and the result showed that the glass transition temperature of the compound increased with the SEBS content.The Avramiequation described the isothermalcrystallization kinetics.Stress-strain curves for PTT and PTT/SEBS composites showed that the elongation at break was enhanced with increasing SEBS content. Poly (trimethylene terephthalate) (PTT) / styrene-ethylene-buthylene-styrene (SEBS) composites were prepared by melt compounding. Polarizing optical microscopy was used to observe the spherulitic morphology and the crystal structure of PTT and PTT / SEBS composites. Scanning electron microscopy was used determine the dispersion and the compatibility of fracture surfaces of PTT and SEBS.The curves of thermalgravimetric analysis illustrated that the thermo stability decreased with increasing SEBS content. differentialscanning calorimetry was used to investigate the crystallization behavior; and the result showed that the glass transition temperature of the compound increased with the SEBS content. The Avramiequation described the isothermal crystallization kinetics. Stress-strain curves for PTT and PTT / SEBS composites showed that the elongation at break was enhanced with increasing SEBS content.