Winding speed is one of the most important process parameters which can change the properties and efficiency of production of the yarns. In this study, the effect of wining speed (2.000-4,000m/min) on the physical properties of partially oriented poly (ethyleneterephthalate) (PET) yarns (POY) filled with carbon black has been investigated. Yarn properties have been characterized by density gradient column, differential scanning calorimetry, X-ray diffraction and stress-strain curves. The crystallinity of yarns increased sharply beyond the winding speed, 3,250m/min due to the stress-induced crystallization. As the winding speed rose, glass transition temperature (Tg), tenacity and crystalline orientation function (fc) of the yarn increased while vice versa is true for elongation. The winding speed of about 3,250m/min was concluded to be the optimum speed in the case of carbon black filled PET POY.