A control curve is calculated for controlling the yarn tension including warp and weft yarn tensions in a weaving loom by comparing a previously determined yarn tension curve with a desired value for the yarn tension curve. The control characteristic is optimized by continuous iteration. A further optimization of the yarn tension curve takes place by taking account of variable parameters in the yarn tension curve, for example yarn breakage analysis, beat-up force of the reed, and/or shed change. The control device for performing the method can be implemented with conventional logic. The method automatically carries out in an advantageous manner for weft and warp yarns a matching to the optimum yarn tension as a function of time on the basis of preselected parameter values.