Abstract: Objective To analyze clinical characteristics and risk factors of pulmonary infection caused by extensively drug-resistant Acinetobacter baumannii （XDRAB）, evaluate antimicrobial therapy and prognosis of XDRAB patients, aiming to provide references for effective prevention and control of nosocomial infection and clinical diagnosis and treatment. Methods Patients with XDRAB isolated from the lower respiratory tract specimens were collected. The number of repeated cases and colonization strains were excluded. The case data were analyzed and summarized by the method of retrospective case analysis. Results A total of 210 XDRAB strains were detected. The distribution of clinical departments was mainly concentrated in the ICU, with 108 cases （51.4%）. Respiratory diseases （OR = 2.294, 95% CI： 1.018-5.170, P < 0.05）, carbapenems （OR = 12.723, 95% CI： 4.585-35.306, P < 0.05）, quinolones （OR= 10.100, 95% CI： 1.950-52.317, P < 0.05）, β-lactam inhibitors （OR = 4.012, 95% CI： 1.659-9.702, P < 0.05） were the independent risk factors for XDRAB infection. The non-improvement rate in the XDRAB group was higher than that in the non-XDRAB group （χ² = 94.500, P < 0.05）. Conclusions The proportion of XDRAB isolated from the ICU is the highest. Respiratory diseases and antibacterial drugs （carbapenems, β-lactam inhibitors, quinolones） are the independent risk factors for XDRAB infection. The prognosis of XDRAB infected patients is poor.