Objective: To investigate the clinical effects of HBV infection on patients with rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE).Methods: This is a prospective study. Thirty patients with RA and 30 patients with SLE admitted to Affiliated Hospital of Hebei University from January 2020 to December 2021 with co-infection of HBV were randomly selected and divided into two groups. Both groups were given anti-HBV treatment. An additional 60 patients with a healthy physical examination during the same period were also selected as a control group. The disease activity, immune function and serum inflammatory factor levels were compared between the RA group and the SLE group before and after treatment.Results: After anti-HBV treatment, DAS scores in the RA group and SLEDAI scores in the SLE group were significantly lower than before treatment(P<0.05). The levels of IgG, IgA, IgM and CD8+ in the RA group and the SLE group after treatment were significantly lower than those before treatment. The levels of CCP, RF, ESR and CRP in the RA group before and after treatment were higher than those in the control group(P<0.05). The levels of ESR and CRP in the SLE group before and after treatment were higher than those in the control group, with statistically significant differences(P<0.05).Conclusion: Patients in the RA and SLE groups after HBV infection have an increased degree of inflammatory response in their organism, an altered normal state of immunoglobulin and T-lymphocyte subsets, and a loss of organism immune function, leading to an increase in disease activity.