Abstract: For the problems that existed in indigo dyeing of denim, i.e., serious loose color, high water consumption in the washing process, too many use of dyestuff and chemicals, high cost of wastewater treatment, the paper optimizes the dyeing process by chemical treatment, discusses the effects of different modification methods on the utilization rate of indigo dyestuff, and compares with the conventional dyeing process. The results showed that the modification of yarns in dyeing pre-treatment and post-treatment can significantly improve the dyestuff utilization rate, reduce the use of dyestuff and chemicals and water consumption in the dyeing process, and reduce the pressure of subsequent wastewater treatment, which is of great reference significance to the current production practice in indigo dyeing of denim.

Key words: denim; indigo dyeing; utilization ratio of dyestuff; water saving