Abstract: Polysaccharides, as a kind of important biological information macromolecules, have been indicated to exist widely in animals, plants and microbials. Currently, the role of polysaccharides in regulating immune system has been generally recognized by the academic community. The immunoregulatory mechanism of polysaccharides on the immune system was mainly via binding to pattern recognition receptors on the surface of immune cells such as Toll like receptors, mannose receptor, Dectin-1, scavenger receptors and complement receptors. Thus stimulating immune cells involves protomoting the phagocytosis of macrophages, regulating the proliferation and transformation of lymphocyte, enhancing the activation of complement system and inducing the secretion of cytokines so as to achieve the immunoregulatory effects. In addition, the regulation of neuroendocrine-immunoregulatory network is regarded as a vital way to exert immunoregulatory effects of polysaccharides as well. The biological activity of polysaccharide and its immunomodulatory effects have always been one of the hot projects. The aim of this article was to review the effects and mechanisms of polysaccharides on immunoregulatory effects related to immune system.