Abstract: Spherulite growth rates and morphological structure changes during the crystallization of PET were investigated using depolarimetry, polarized microscopy(PLM) and small angle light scattering(SALS). The unusual behavior of spherulite growth rate curves under various conditions in the crystallization of PET was observed by depolarimetry. A plot of depolarised light versus crystallization time indicates that there is a slight reduction in the crystallinity at higher temperature. It is suggested for this phenmenon that partial melting and recrystallization of the crystallite occur at higher temperature. In other words, imperfect crystallites are melted and changed into more perfect forms (better crystal lattice, larger crystal size). Observations with PLM have confirmed the explanation suggested. Three types of spherulites patterns (usual, unusual and complex) in PET under dif-ferent crystallization temperatures have been observed with PLM. The usual spherulites formed at lower temperatures, while unusual spherulites formed at higher temperatures.The results agreed with Hv patterns of the SALS.