Dynamic processes of isothermally cold-crystallized poly(trimethylene terephthalate) (PTT) was investigated by fluorescence spectroscopy of its amorphous region. The key issue lay in the fact that the emission at 390 nm originating from the main chain phenylene ring in the amorphous phase was correlated to the cold-crystallization. A reduction ill this emission peak intensity corresponded to a gradual transition of the phenylene ring in the amorphous to crystal region. Accordingly, molecular chain movement and structure evolution of PTT in the course of cold-crystallization were, carefully revealed. The experimental results indicated that the kinetics parameters measured by the fluorescence spectroscopy method are in good agreement with those by differential scanning calorimetry (DSC). What is more, the former was capable of providing, detailed information about structural variations during cold-crystallization, for example, molecule arrangement in induction phase.