Abstract: OBJECTIVE To study the combined antibacterial effect of Reduning combined with cefoperazone/sulbactam sodium and tigecycline on extensively drug resistant Acinetobacter baumannii（XDRAB）. METHODS Total of 88 patients with XDRAB pneumonia admitted to the 987 th Hospital of the People's Liberation Army Joint Logistic Support Force between May 2017 and Mar 2020 were divided into the study group and control group by using random number table method, 44 cases in each group. On the basis of conventional treatment, the control group was given intravenous administration of cefoperazone/sulbactam sodium and tigecycline, and the study group was given intravenous administration of reduning combined cefoperazone/sulbactam sodium and tigecycline. Bacteria clearance rates, total effective rates, body temperature recovery time, cough relief time, infection control window appearance time, acute physiology and chronic health scores（APACHEⅡ）, clinical lung infection（CPIS） scores, inflammatory response related indicators including C-reactive protein（CRP）, white blood cell count（WBC）, procalcitonin（PCT）, interleukin-6（IL-6）, tumor necrosis factor-α（TNF-α）, humoral immunity related factors such as immunosphere Protein M（IgM）, IgG and IgA, cellular immunity related factors including CD₃⁺, CD₄⁺, CD₄⁺/CD₈⁺, natural killer（NK） cells, and drug safety between the two groups were compared. RESULTS The bacterial clearance rate and total effective rate in the study group were significantly better than those in the control group（P＜0.05）. The body temperature recovery time, cough relief time, and appearance time of infection control window in the study group were significantly shorter than those in the control group（P＜0.05）. After treatment, the APACHEⅡ and CPIS scores, CRP, WBC, PCT, IL-6, and TNF-α in the study group were significantly lower than those in the control group（P＜0.05）. After treatment, IgM, IgG, IgA, CD₃⁺, CD₄⁺, CD₄⁺/CD₈⁺, and NK cells in the study group were significantly higher than those in the control group（P＜0.05）. There was no significant statistical difference in the incidence of adverse reactions between the two groups. CONCLUSION Reduning combined with cefoperazone/sulbactam sodium and tigecycline can improve the combined antibacterial effect by reducing inflammation and regulating immune function, which can promote the prognosis of patients with XDRAB pneumonia with certain safety.