Carbohvdrates have many important biological functions in organism. It has been demonstrated that structural characteristics of carbohvdrates provide important clues for the understanding of cell and molecule recognition process where sugar is mainly involved in. It is concentrated on the concepts of oligosaccharide structure,the latest theoretical development of this subject,as well as some methods often used in this field.It is generally considered that one of the theoretical directions is to exhibit the interactions between oligosaccharides and proteins, and the structure and function of oligosaccharide in glycoprotein.