The pathogenicity of duck virus hepatitis (DVH) caused by duck hepatitis virus A virus type 1 (DHAV-1) is very strong.Once ducklings were infected with DHAV-1 the mortality rate could even reach to 100%.Unfortunately,to date there is still no effective drug treating DVH in clinic.What was more,the morbidity and mortality are high in ducklings which have been immunized with attenuated vaccine.So,the research and development of anti-DVH drugs are imminent.In recent years,because of the strong biological activity of Chinese herbal medicine,many investigators attentions of drug development shifts to plant extracts and their derivatives.In the theory of traditional Chinese veterinary medicine,DVH is a kind of blood-heat disease,and the principle of treatment is blood-cooling and heat-removing.Bush Sophora Root is a blood-cooling and heat-removing drug as well as owns a wide range of antiviral activity.Therefore,we studied the anti-DVH activity and mechanism of the main active ingredient of Bush Sophora Root,Bush Sophora Root polysaccharide (BSRPS),and its sulfate,sulfated Bush Sophora Root polysaccharide (sBSRPS).Through analyzing the anti-DVH activities of BSRPS and sBSRPS by in vitro and in vivo tests,we found that both BSRPS and sBSRPS owned fine curative effect and the effect of sulfate was stronger.Then the antiviral mechanisms of BSRPS and sBSRPS were studied by direct antiviral link (virus inhibition) and indirect antiviral link (anti-oxidative and immno-enhancing activities).Results showed that BSRPS was able to reduce DHAV-1 replication and sBSRPS was able to reduce DHAV-1 replication and release.Both BSRPS and sBSRPS were able to strengthen the anti-oxidative and immno-enhancing activities of ducklings which were infected by DHAV-1.And to BSRPS,both these two activities played roles in treating DVH.But to sBSRPS,only immuno-enhancement ability of sBSRPS was imperative for its curative effect on DVH.