[Abstract] Objective:Conducted at the research site in Nantong City, this study aims to investigate the current situation and characteristics of HIV/HBV co-infection among HIV-infected individuals, as well as to analyze the effectiveness of antiviral therapy and its influencing factors for HIV/HBV co-infected patients.Methods:The study selected newly diagnosed HIV/AIDS patients in Nantong City from January 1st, 2016, to December 30, 2021, as the research subjects. Based on the results of hepatitis B surface antigen (HBsAg) testing, the patients were categorized into two groups: the HIV mono-infection group and the HIV/HBV co-infection group. The study compared the HIV infection characteristics of the two groups before antiviral therapy, analyzed the virological suppression and CD4+ T lymphocyte (CD4) changes after antiviral therapy, and evaluated the improvement of immune function and its influencing factors.Results: A total of 1830 cases were included in the HIV mono-infection group, and 135 cases were included in the HIV/HBV co-infection group. HIV/HBV co-infection led to more severe immune impairment before antiviral therapy compared to HIV mono-infection. After receiving antiviral therapy, both the HIV mono-infection group and the HIV/HBV co-infection group showed a gradual increase in CD4 count, and the virological suppression rate reached over 90% in both groups after two years of antiviral therapy. Univariate and multivariate logistic regression analyses showed that increasing age, initial CD4 count <200 cells/μL, and initial HIV RNA ≥4.5 log (copies/ml) were risk factors for immune reconstitution. There was an increasing trend in the rate of favorable immune reconstitution with prolonged treatment time. Co-infection with HBV exacerbated immune impairment in HIV-infected individuals before antiviral therapy and may affect immune reconstitution. Conclusion: HBV infection can worsen immune damage in HIV-infected individuals. The current antiviral therapy strategy for HIV/HBV co-infection effectively suppresses dual infection and benefits immune reconstitution in HIV/HBV co-infection. However, there are insufficiencies in antiviral therapy and efficacy monitoring in patient management, highlighting the need for further standardization of clinical diagnosis and treatment activities.