As the economy develops, the living conditions of the people have been improved accordingly. The starting point is air permeability. We discuss the influence of the position of tuck on the air permeability of knitted fabrics. The result shows that the major causes are materials and structures. The air permeability increased with the centering of tuck point. The more the filament of yam has, the more the surface area is. But the more the region of covering is, the less the air permeability is. We can control the air permeability by choosing the materials and structures. The air permeability of the elastic knitted fabrics was changed with the shrinkage of weaving. The trend resulted from the changing of drawing ratio was same, because the shrinkage of the structure was limited.
