HA is a natural biotic component, widely existing in skin and any other tissue. It has outstanding moisture keeping ability, thus called Natural Moisturizing Factor (NMF) in the world. It is the best component used in cosmetics for moisture keeping in the nature. When HA applied to the skin, macromolecular HA can form a thin air permeable layer and keep the skin smooth and moist, and protect the skin from bacteria, dust, and ultraviolet ray. Low molecular weight HA can penetrate into corium and slightly enlarge blood capillaries, speed circulation of blood, improve intermediary metabolism and nourishment absorbing ability of skin, thus eliminating wrinkles, increasing skin's elasticity and delaying its aging. HA as well can further hyperplasia of epidermis cell, clean oxygen free radical, prevent and rehabilitate breach of skin.