Abstract: Different sulfate group contents of polysaccharides from Gracilaria lemaneiformis(PGL),namely refine polysaccharides(RPGL),purified polysaccharides(GL-1,GL-2 and GL-3),desthio-PGL,and sufation polysaccharides(S1,S2 and S3),their anti-influenza virus H1-364 activities and the effects on sulfate group content on antiviral activities of H1-364 were studied by MTT method. Results showed that different polysaccharides from Gracilaria lemaneiformis have anti-influenza virus H1-364 activities,and RPGL’s inhibiting effect is the best of them and its max virus inhibition ratio is 88.82%. The antiviral abilities of the polysaccharides are better when sulfate group content is higher within limits. While sulfate group content is near 13%,the polysaccharides samples get the best antiviral abilities,while sulfate group content is higher or lower than 13%,the antiviral abilities reduce.

Key words: polysaccharide from Gracilaria lemaneiformis, sulfate group, antivirus activity