[Background] Ganodema lingzhi Sheng H. Wu, Y. Cao & Y.C. Dai. is a widely regarded medicinal and edible fungus. Spectacularly, it was used as a traditional medicine and health food in China for thousands of years and the cultivation of G. lingzhi has been expanding rapidly recent years. Polysaccharides are considered to be the most important active ingredient in G. lingzhi. [Objective] This article focused on the extraction, purification, structure and immunoregulatory effects of a novel polysaccharide purified from the fruit bodies of G. lingzhi. [Methods] The polysaccharides of G. lingzhi (GLP) were extracted with boiling water and purified by DEAE cellulose-52 column and Sephadex G-100 column. The high performance gel permeation chromatography (HPGPC), PMP derivatization and FT-IR method were used to analysis molecular weight, monosaccharide composition and backbone structure, respectively. The splenocyte proliferation was analysed by MTT assay. The potency of polysaccharides on the phagocytosis and cytokine secretion of RAW 264.7 cells was determined by commercial kit. [Results] The molecular weight of GLP was 1.93×104 Da, the monosaccharide composition of GLP was mainly composed of glucose, galactose and mannose, with a ratio of 3.3:1.3:1.0. The anomeric carbon of GLP has a β configuration. GLP resulted in a significant increase of lymphocyte proliferation and could also enhance the effect of Con A-induced T lymphocyte proliferation and the stimulation index of LPS-induced B lymphocytes. In addition, the phagocytosis and cytokine secretion of RAW 264.7 cells can be promoted by GLP. [Conclusion] GLP may be developed as a potential immunoregulatory drug.