This study was carried out to investigate the thermal and physical properties of nylon 6 POY which was taut-annealed under various conditions. On the basis of the DSC curves, it was found that the origin of the double melting peaks of nylon 6 POY was due to the coexistence of crystals with different thermal properties. Among the scanning rates of 5$^{circ}C$/min, 20$^{circ}C$/min and 40$^{circ}C$/min, the last was best to study the effect of annealing on the melting behavior of nylon 6 POY because it was able to eliminate or minimize the programmed heating effect during DSC analysis. Crystallinity and birefringence of annealed specimens increased as the treatment temperature and time increased. Tenacity at break increased as the temperature increased up to 180$^{circ}C$, but decreased as the time increased. Elongation at break decreased as the annealing temperature and time increased.