With the increasing application and further research of polysaccharides, the development of new green techniques arouses wide attention from academia and industry. Due to special physicochemical properties, ionic liquids (ILs) have been applied widely in carbohydrate chemistry mainly as green and efficient chemical solvents/catalysts for the degradation, synthesis and modification of polysaccharides. Their roles and potential should be fully understood by researchers in carbohydrate chemistry. Because of their unique characters different from other traditional reagents, it is necessary to explore and review the uses, performance, advantages and disadvantages of ILs in detail. This paper focuses on the new advances in the application of ILs to the degradation of cellulose together with the synthesis and modification of polysaccharide; those important findings and systematic comparison were also introduced. Finally, the key conclusions were provided for related researchers and their future was analyzed, and this review was supposed to be a useful reference in the cross-subject area of glycochemistry and green chemistry.