To study the in vivo anti-viral effect of a Chinese drug, composite Shuangcao Anti-Jaundice Granule No. 1(SCG-1), on duck hepatitis B virus (DHBV). Guangzhou brown spot ducklings infected with DHBV were used as the hepatitis B animal model, for which, 1-day old ducklings were infected with DHBV. Positive DHBV-DNA in ducklings sera were detected 13 days after the infection, and then SCG-1 was given for 14 days and DHBV-DNA was detected by dot-blot hybridization test. After medicated with SCG-1 [10 g/(kg.day) and 5 g/(kg.day)] 7 days and 14 days, optic density value (OD value) of DHBV-DNA in ducklings' sera were obviously lower than that before treatment, there was significant difference. But rebound phenomenon appeared in both groups 3 days after stopping medication (P < 0.05). SCG-1 could inhibit the replication of DHBV-DNA in Guangzhou ducklings.