Abstract: Objective: Anti- proliferation and antioxidant activities of polysaccharides from Coelomactra antiquata ( PCA) on human esophageal carcinoma EC-9706 cells in vitro were observed. Methods: EC-9706 cells were cultured with different concentration of PCA in vitro.The proliferation inhibiting of esophageal carcinoma cells were determined by MTT assay.Furthermore, effect of different concentration of PCA on superoxide dismutase ( SOD) , catalase ( CAT) of esophageal carcinoma cells and mouse hepatocyte were measured, meanwhile, total antioxidant activity ( T- AOC) and scavenging effect of hydroxy radical (·OH) of culture supematan were evaluated. Result:EC-9706 cell proliferation rate gradually increased with the polysaccharides concentration and time increased.PCA could enhance the activities of cells cultured in vitro.Under the condition of same polysaccharide concentration, the activities of SOD, CAT, T- AOC and scavenging ·OH of mouse hepatocyte were all higher than esophageal carcinoma cells. Conclusion: PCA could restrain proliferation of human esophageal cancer cells, and enhance the activities of cells cultured in vitro.