Yarns play a dual role in the process of garment making and process-cycle. Yarns are both the final product of spinning mills and raw materials of weaving factories, which can be packaged and sold as both semi-manufactures and finished products. Yarn is the middle part of fabric which is made of fiber. The concept of yarn gives us the inspiration that the yarn is made up of fiber and the fiber is tightly combined in a certain way. Therefore, understanding the basic knowledge of yarn and mastering the main varieties and properties of yarns are very important for selecting yarn reasonably and effectively expressing the appearance and surface properties of fabrics and garments. Generally, the process flow of garment fabric is: fiber (twisting)- yarn (prepared for weaving)- fabric (sewing)- clothing.