Objective To study the effect of cartilage polysaccharide on S_(180)-bearing mice and its anti-tumor mechanism.Methods The S_(180)-bearing mouse model was prepared and treated by i.p.injection of cartilage polysaccharide.The tumor cells morphology was examined by light microscopy.The cell cycle was analyzed by flow cytometry,and apoptotic rate was determined by TUNEL assay.The expression of Fas and PCNA proteins was studied by immunofluorescent staining.Results The survival rate of S_(180)-bearing mice was significantly increased by cartilage polysaccharide treatment in comparison with that of control group.Cell shrinkage,nuclear condensation and apoptotic bodies were detected by morphological observation.The cell cycle of S_(180) cells was arrested at G_2/M phase. The expression of Fas protein was increased and PCNA expression was decreased at 24 h after cartilage polysaccharide treatment.Conclusion Cartilage polysaccharide induces apoptosis of S_(180) cells by cell cycle arrest and influences the expression of Fas and PCNA proteins,and inhibits tumor cell growth,and prolong survival time of S_(180)-bearing mice.Those findings indicate that cartilage polysaccharide might become a novel anti-tumor agent in future.