The effect of self-seeding nucleation on the crystallization behavior ofpoly(trimethylene terephthalate) (PTT)was studied.Differential scanning calorimetry (DSC) indicated that the crystallization temperature of PTT notably increased after self-seeding nucleation.Avrami equation was applied in the analysis of the isothermal crystallization process of PTT.The resulting average value of the Avrami exponent at n = 3.34 suggests that primary crystallization may correspond to a three-dimensional spherulitic growth.Selfseeding nucleation,leading to a decrease in active energy for crystallization and chain folding work,promotes the overall crystallization process of PTT.