In the weaving process the variations of the warp yarn tension cause irregularities of the weft density of the woven fabrics. Due to the fact that warp yarn tension varies in a great extent depending on the ratios of the take-up and the let-off speed, it is necessary to regulate the speed of let-off in relation to that of take-up operation for keeping warp yarn tension in a certain range allowable for the fabric quality. Therefore it is indispensable to analyze the dynamic characteristics of the take-up and let-off system for obtaining the weaving process optimally. In this research it was tried to get the dynamic characteristics of the let-off/take-up process theoretically, and the behavior of the warp yarn tension was simulated on the basis of the mathematical model, depending on the let-off and take-up speed, tensile properties and feeding tension of the warp yarns. From this research the following results could be obtained: 1) dynamic warp yarn tension can be described by a differential equation, however, nonlinearly with respect to the take-up speed, 2) the behavior of warp yarn tension has a characteristics of a 1st order system in the case of a constant take-up speed, and 3) variations of warp yarn tension can always occur when take-up speed changes.