The fruiting body of Hericium erinaceus has been used to treat digestive system disorder-related diseases for over 2000 years in China. A novel polysaccharide, HEFP-2b, was obtained from H. erinaceus fruiting bodies. Physical and chemical analysis showed that HEFP-2b consisted of fucose, galactose, glucose, and mannose in molar ratio of 11.81:22.82:44.28:21.09, and that its molecular weight was 3.252 × 104 Da. The backbone of HEFP-2b consisted of →6)-linked-α-D-Glc p -(1→ and →4)-β-D-Gal p -(1→ and →3,6) -α-D-Man p linkage, with two side-branching units of (1→ and →6)-β-D-Gal p and (1→ and →4)-α-D-Man p , terminated by Glc and Fuc. The results of the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and cell cycle arrest experiments revealed that HEFP-2b considerably inhibited the growth of colon cancer cells (HCT-116) in vitro. The growth inhibitory effects of HEFP-2b correlated with their ability to arrest the cell cycle at the S -phase. Our results will provide valuable information for future studies on HEFP-2b as a novel health-promoting functional food ingredient that can be used for treating colon cancer. • Hericium erinaceus , as a medicinal fungus with well-known health-promoting effects • A novel polysaccharide with 22.82% of Gal, HEFP-2b, was obtained from H. erinaceus. • HEFP-2b was able to effectively inhibit the growth of HCT-116 and DLD1 cells. • HEFP-2b could induce arrest of cell cycle at S -phage in the colon cancer cells. [ABSTRACT FROM AUTHOR]