The purpose of this study was to examine the effect of heat-setting temperature and time and winding tension on the physical properties of polyester filament yarn during heat setting. The sample used was polyester 75 D/36F SD. The sample was treated with temperature of 80-12$0^{circ}C$ and time of 20-120 min by the use of vacuum dryer with the tension of 5-35 g. The tensile characteristics including tenacity, elongation, and initial modulus and boil-off shrinkage of treated samples were examined. In addition, thermal stress analysis including thermal stress, initial temperature of shrinkage, and peak and rupture temperature of treated samples was evaluated. The results were as follows. 1) As heat-setting temperature and time increased, there were little change in tenacity and elongation of treated samples, but initial modulus, boil-off shrinkage, and thermal stress decreased and initial temperature of shrinkage and peak temperature increased. 2) As winding tension increased tenacity, elongation, initial modulus, boil-off shrinkage, and thermal stress increased, but initial temperature of shrinkage and peak temperature decreased.