Objective The extraction process of polysaccharide in snail will be analyzed to study on polysaccharide in snail physicochemical property and the effect of it against tumor cells in vitro. Methods The content of polysaccharides is determined by phenol-sulphoacid method， the protein content of polysaccharides is tested by ultraviolet spectrometry， UV and the sulfate of polysaccharides is detected by electrolysis. With HCT-8 colorectal carcinoma and Hela cell line being the cell model in vitro， the polysaccharides of snail with different concentration and 5-Fu are to interact with cancerous cells. After 72 hours， comparing with the cells with no drug， through detecting the cell activity by MTT method， the rate of cell inhibition will be calculated. Finally， evaluate the anti-tumor activity of polysaccharide of snail in vitro according to all the above results. Results The amount of polysaccharides is 86.26%， containing low protein and sulfate. The polysaccharide can inhibit the proliferation on Hela cell line and HCT-8 colorectal carcinoma cell line， but weak in the latter. Conclusion The polysaccharides of snail show anti-tumor activity， but have certain selectivity or different inhibition mechanism against different types of tumor cells.