Hollow fiber is widely used and has good elasticity. It has the advantages of fluffy, warm keeping, good air permeability, pressure resistance, anti knot deformation, light weight, strong tensile strength, water washing resistance, not afraid of moths, mildew proof and moisture-proof. The heat preservation rate is more than 60% higher than that of cotton fiber, and its service life is more than 3 times longer than that of cotton fiber.