In order to investigate the change of the fine structure by drawing of POY PET filaments, each sample was drawn at below TR(75$^{circ}C$), TR(82$^{circ}C$), and above TR(9$0^{circ}C$). to the desired draw ratio. The change of the fine structure caused by different drawing conditions (draw ratio and temperature) was studied by measuring crystallinity, X-ray diffraction, dynamic viscoelasticity, birefringence and thermal behaviour. The conclusions obtained from this study are as follows 1. At the same drawing temperature, the degree of crystalliniter hifringonce, TR, Tm, and heat of fusion(AUm) increased with the draw ratio. 2. At the same drawing temperature, the X-ray diffraction pattern displayed sharper peaks with increasing draw ratio, while at the same draw ratios(D/R: 2 and D/R: 3), the X-ray pattern was sharper for the sample drawn at 75$^{circ}C$ than that drawn at 82$^{circ}C$ and 9$0^{circ}C$. 3. At the same drawing temperature, the decrease in the intensity of the tan 6 peak and the shift of the peak position toward higher temperature were observed with increasing draw ratio. At the same draw ratio (DIR: 3) , the lateral order of the amorphous region seemed to increase appreciably for the sample drawn at 75$^{circ}C$ than that drawn at 82$^{circ}C$ and 9$0^{circ}C$