Objective To detect and analyze the HBV-related indexes in the urine of HBV transgenic mice and further understand the biological characteristics of transgenic mice, and to clarify the tissue sources of HBV-related indexes. Methods HBV-related indexes in the urine of transgenic mice were tested using enzyme-linked immune sorbent assay (ELISA) and fluorescence quantitative PCR (real-time RCR). The tissue sources were confirmed by several experiments, i.e. hydrodynamic transfection of mice, RNA interference to inhibit HBV-expression in the transgenic mice, and to infect normal mice with HBV-positive serum from patients. Results Expression of HBsAg, HBeAg and HBV-DNA was present in the urine of transgenic mice, of which the HBsAg expression level was high (6674±619.8 IU/mL), but lower than that in the serum (16470±2704 IU/mL). The level of HBsAg expression in the urine of male mice was higher than that in female mice. The level of HBeAg expression in the urine was lower and the HBeAg positive rate of urine was higher than that of blood, and the levels of HBeAg expression showed significant inter-individual and inter-sexual differences. HBV-DNA level reached 10³-10⁵ copy/mL in the urine, but no related antibody expression was detected. The experiments such as hydrodynamic infection test indicated that the HBV-related indexes in the urine are derived from replication in the kidneys rather than secreted from the liver, entered into the blood circulation, and discharged from the urine. The kidneys are an independent expression site of HBV. Conclusions The expression of HBV-related indexes is present in the urine of transgenic mice and it is a long-term expression along with the age in months, of which the expression levels of HBsAg and HBV-DNA are rather high and stable. HBsAg titer in the urine of the male mice is higher than that of female mice. HBeAg expression level in the male mice is more stable compared with that in female mice. No expressions of various kinds of antibodies have been found in the urine. The kidneys are an independent expression site of HBV.