One water-soluble polysaccharide (ASPS), with four molecular weight distributions of 74, 3.8, 4.5, 2.3 x 10(4) Da, was isolated from the root of Acanthopanax senticosus and the yield was 4.8% (w/w). ASPS was composed of arabinose (51.4%), glucose (24.5%), galactose (10.2%), xylose (5.7) and galacturonic acid (4.9%). Effects of ASPS on the proliferation, apoptosis and Wnt/β-catenin signaling pathway were investigated in human hepatocellular carcinoma cell line HepG2 cells. The study showed that ASPS could inhibit the proliferation, increase the apoptosis rate in HepG2 cells; meanwhile, ASPS could increase the proportion of cells in G0/G1 phase, decrease the proportion of cells in S phase and G2/M phase, and elevate the expression level of β-catenin, C-myc and Cyclin D1 proteins in HepG2 cells. These results indicate that ASPS has a certain inhibition on the proliferation, can induce the apoptosis and G0/G1 phase arrest in HepG2 cells, and the mechanism may be related to the inhibition of ASPS on the activation of Wnt/β-catenin pathway HepG2 cells.