Abstract: In this review, the present status of the molecular and physiological mechanism of the differentiation and development of cotton fiber is discussed, in which the molecular and physiological mechanism of the producing of the cell turgor, loosening of the cell wall, synthesis of the composition molecules and their incorporation into cell wall, signal of the starting of secondary wall thickening, cellulose biosynthesis, and layout of cellulose microfibril regulated by cytoskeleton are introduced in detail. Some views on its prospects are further suggested.