This study presents a flexible and highly stretchable textile circuit line for the signal and power transmission of smart clothing systems that provide wearing comfort and high mobility to where’s. A textile based circuit network on smart clothing requires 30% stretch ability so as not to constrain body movement. The advantages of a textile band type transmission line is the easy configuring of several separate transmission lines on a single band to construct a sensor module network. Conductive transmission line yarns have to be protected from deformation when textile transmission lines are stretched according to body movement. To ensure the elastic property of the smart clothing, textile transmission lines need to stretch more than 30% using the additional spandex yarns in warp. Four strands of conductive yarns were inserted in a single transmission line and each transmission line indicated 0.03Ω/cm in resistance. The resistance change rate of the textile transmission line during elongation was measured using a universal testing machine (Instron 5543) and Milliohmeter (Agilent 4338). The resistance of the transmission lines unchanged until breakage occurred at the 140% strain level. Resistance started to change at the 180% strain level where conductive yarns start to deform and break. In conclusion, the proposed textile transmission provides a comfortable wearing sensation that maintains a stable electrical performance during any type of body movement and is suitable for the wearable circuit of a highly stretchable smart wear system.