The coiled stability of velcro directly affects quality of images acquired by the visual inspection system, thereby affects the accuracy of the defects identification. Mechanical design theory and modern control methods have been used to design transmission parts in appearance vision inspection system for velcro, and achieved the stable transmission of inspection system and the constant linear speed inspection of Velcro were achieved. Through rigorous mathematical derivations, the variation of the radius in constant linear speed detection was obtained, thus the control method of constant linear speed was analyzed and simplified, the formula of motor driving frequency was obtained, a theoretical basis was provided to closed loop constant linear speed control.