Ardisia chinensis Benth is a medicinal plant traditionally used in the area of Yao minority in Southern China. The in vitro antiviral activities of extracts and fractions from Ardisia chinensis were tested by the cytopathic effect (CPE) reduction assay in the present study. As a result, both the aqueous extract and the 95% ethanol extract of Ardisia chinensis showed in vitro antiviral activity against Coxsackie B3 (Cox B3) virus to different extents, and the aqueous extract possessed more potent activity than the ethanol extract. Bioassay-guided fractionation revealed that the antiviral activity of Ardisia chinensis was attributed mainly to its high polar fractions, and finally identified to be a polysaccharide. The Ardisia chinensis polysaccharide (ACP) fractionated from the aqueous extract exhibited a significant antiviral effect against Cox B3 with a 50% inhibitory concentration (IC(50)) of 3.9 microg/mL and a selective index (SI) over 256. Preliminary characterization indicated that ACP is a neutral polysaccharide in which d-glucose is the major component. The average molecular weights of ACP were determined to be 40037 Da (Mw), 28297 Da (Mn) and 33758 Da (Mp) by gel permeation chromatography.