Poly(trimethylene terephthalate)/mesoporous silica SBA-15 composites were prepared by in situ hybridization for the crystallization study. The results show that SBA-15 particles are well compounded with PTT, forming nanostructured composite system. Although the addition of SBA-15 particles results in an evident decrease of PTT molecular weight, those well dispersed mesoporous particles can compensate effectively for the property degradation of PTT. Besides, the addition of SBA-15 particles has large influence on the crystallization of PTT. The composites show higher crystallization temperature and rate than that of the neat PTT. But the presence of SBA-15 impedes PTT chain segment movements somewhat. In comparison with neat PTT, therefore, the composites present lower folding surface free energy and higher diffusion activation energy. The kinetic analysis results elucidate that the crystallization rate of PTT is dominated by the nucleation item instead of the growth one. (c) 2013 Elsevier B.V. All rights reserved.