Water vapor through the fabric, there are mainly three path: one is the water vapor through the fabric of microporous diffusion; 2 it is hygroscopic fiber itself, and low vapour pressure in the fabric a transgression; 3 it is to a large number of water molecules will produce condensation, and spread by capillary action, more evaporation at low water vapor. Through the fiber moisture absorption, water vapor transmission, escape, and the fabric used in the fiber, moisture content, the pore and the degree of expansion and fibre channel. Functional fabric moisture absorption perspiration asked not bibulous the fabric with water and dry quickly. Polyester fiber has high crystalline molecular chain structure, this structure makes polyester in hygroscopicity water imbibition is small, the poor permeability, but that just makes it has very excellent ability of quick drying. Natural fibers such as cotton, fiber structure existing in the large gap in the moisture absorption performance is excellent, but the expansion of the water absorption after effects strengthened the grip force of water, resulting in the defect of the quick drying performance. Generally speaking, the functional fabric moisture absorption perspiration is the use of fiber surface micro grooves generated by capillarity make sweat absorption, diffusion, and transfer the core role, rapid migration to the surface of the fabric and volatile, so as to achieve the purpose of guide wet quick dry. Capillary effect, as it were, a method is the most common and most intuitive, can show the fabric absorbent ability and diffusion ability. Others will moisture absorption perspiration fiber called can breath, it is focus on moisture absorption, perspiration and underwear comfortable functional fibers.