Abstract: Objective 　To investigate new antitumor selenium compound by studying the effect of Eucheuma Polysaccharide ( EP), inorganic selenium compound--sodium selenite (Na₂SeO₃) and organoselenium compound-Eucheuma polysaccharide selenide (SeEP) on the proliferation of human larynx epidermoid carcinoma cell line Hep-2 in vitro. Methods 　HEp-2 cells were incubated with EP, Na₂SeO₃ and SeEP separately at different concentrations for 72 hours. The cell viability was measured by MTT colorimetric assay. Results 　The inhibitory ratios of SeEP are significantly higher than that of EP or Na₂SeO₃ at some polysaccharide and selemium concent rations ( P < 0. 05), and reached to 71. 53 % at 4000μg/ ml. The IC50s of SeEP are 1805μg/ ml by polysaccharide and 7. 0μmol/ L by selenide, which are lower than 3034μg / ml of EP and 9. 0μmol/ L of Na₂SeO₃respectively. Conclusion 　SeEP shows an antitumor effect on HEp-2 cells, and it is more potent than both EP and Na₂SeO₃