Objective:In this article, we analyzed and discussed the clinical characteristics and S region gene sequencing of hepatitis B virus in HBsAg anti-HBs coexistent patients.Methods:Data of 5 serologic markers of hepatitis B and quantitative result, liver function and HBV DNA load of HBsAg positive patients were collected, and their basic clinical information were recorded. According to the positive and negative result of Anti-HBs, the clinical and virological characteristics of these two groups were analyzed. At the same time, among 17 320 patients with HBsAg positive HBV infection, 994 cases were tested by gene sequencing. The S region amino acid mutation, site mutation detection rate and genotype of 994 HBV infected patients with gene sequencing were statistically analyzed.Results:The positive rate of HBsAg and Anti-HBs was 4.36% (756/17 320). HBV-related cirrhosis in HBsAg+ /Anti-HBs+ group (19.71%) was significantly higher than that in HBsAg+ /Anti-HBs-group (15.94%), while chronic hepatitis B (62.04%) was significantly lower than that in HBsAg+ /Anti-HBs-group (67.06%). At the same time, the positive rates of HBsAg-quantification (QN) and ALT in HBsAg+ /Anti-HBs+ group were significantly lower than those in HBsAg+ /Anti-HBs-group, the positive rate of HBeAg was significantly higher than that in HBsAg+ /Anti-HBs-group, and the HBV DNA was higher than that in HBsAg+ /Anti-HBs-group, but the difference was no statistical significance. Gene sequencing was performed in 994 HBV patients. Genotype C (81.79%) had the highest proportion, genotype B (17.40%) was the second, and genotype D (0.80%) was the least in two groups. In genotype C HBV infected patients, the detection rate of sP120Q/T/A/S mutant in HBsAg+ /Anti-HBs+ group was significantly higher than that in HBsAg+ /Anti-HBs-group. Meanwhile, regardless of genotype B or C or overall comparison, the detection rate of sG145A/E/K/R mutant of HBV infected patients in HBsAg+ /Anti-HBs+ group was significantly higher than that in HBsAg+ /Anti-HBs-group, these differences were all statistically significant.Conclusions:The hepatitis B patients with coexistence of HBsAg and Anti-HBs were more likely to develop cirrhosis, and the hepatitis B patients with HBV gene sequencing results were mainly type C2. The drug resistance variation of S-region sP120Q/T/A/S and sG145A/E/K/R mutants of patients with HBV infection is an important reason for the coexistence of HBsAg and Anti-HBS.