spandex stretch yarn, denim varieties have developed into a new field, can make jeans both close and comfortable, with bamboo or different colors, so that the product is more suitable for denim fashion, personalized consumer demand, so it has great potential for development. The elastic elongation is generally 20% to 40% elastic elongation. According to the design of the weft structure size of the fabric, the weft structure on the fabric has a smaller tightness and greater elasticity. On the other hand, the conditional tension strength of the fixed weft yarn has a smaller elasticity. The weft density is to a certain extent, and even loses elasticity. In addition, the shrinkage rate of the finished fabric of stretched denim is generally more than 10%, and some even as high as 20%. The unstable width brings great difficulties to garment production. The solution is not to do elastic stretch in product design. Through large, generally from 20% to 30%, that is, to maintain a certain latitude, the appropriate method of increasing tension is adopted when the tissue and tension increase, and the wide shrinkage range is large, so as to obtain a lower residual shrinkage of the finished weft yarn; Another solution is to heat-treat the heat-treated elastic denim to obtain a more uniform width and more stable, low weft shrinkage, and meet the requirements of garment production.