Spandex is the abbreviation of polyurethane fiber, which is an elastic fiber. Spandex is generally composed of multiple filaments, generally 10d/ root, and now there are 15d/ root, or even 20D/ root. The less the theoretical number, the better the uniformity. DMAC, the production solution of dry spinning, is harmful to human liver because there is less chance of morphological overlap, and the content of 10d/ root is generally controlled at 0.5mg/kg. When producing spandex, special attention should be paid to winding tension, yarn count, breaking strength, elongation at break, forming degree, oil adhesion and elastic recovery rate. These problems directly affect knitting, especially the knitting production of one-sided cloth.