To examine the effect of Gankang Suppository on duck hepatitis B virus （DHBV）, the serum biochemistry and hepatic histology in an animal model of DHBV infection, a model of DHBV infection was established by infecting 1-day-old Yingtaogu ducklings with DHBV-positive serum. The successful model was confirmed by PCR assay and 48 ducklings infected with DHBV were randomly divided into 3 groups： a Gankang Suppository treatment group, an acyclovir （ACV） group and a DHBV model group （control）, with each group having 16 animals. All the animals were given the medicines for 4 weeks in a row. The serum of the animals was taken 14 and 28 days after the medica- tion and 7 days after drug discontinuation. Real-time PCR was performed to detect the copy numbers of DHBV DNA in the serum. ALT and AST were dynamically monitored. The ducklings were sacrificed on the 7th day after the discontinuation of the treatment and livers were harvested and examined for inflammation and degeneration of liver cells by using HE staining. The results showed that on day 14, 28 after the treatment and day 7 after the withdrawal, the logarithmic values （log） of DHBV DNA copy numbers in ducklings of Gankang Suppository treatment group were significantly lower than that before the treatment （P=0.0092, P=0.0070, P=0.0080, respectively）. Compared with DHBV model control group, the ALT level was significantly decreased （P=0.0020, P=0.0019, respectively） on day 28 after the treatment and on day 7 after the withdrawal. The AST level was also reduced on day 14 after the treatment （P=0.0298）. Compared with the ACV control group, the level of ALT was lower on day 7 after the withdrawal （P=0.0016）. Histologically, the hepatocyte swelling, vacuolous degeneration and acidophilic degeneration in Gankang Suppository treatment group were alleviated 7 days after the withdrawal as compared with model control group （P=0.0282, P=0.0084, P=0.0195, respectively）. It is concluded that Gankang Suppository can effectively suppress DHBV
