Objective To investigate the diagnosis and treatment of Acinetobacter baumannii (AB) lower respiratory tract infection (LRTI) in intensive care unit(ICU), and provide reference for the prevention and treatment. Methods Clinical data of patients who were isolated AB in a general ICU of a tertiary first class hospital from September 2017 to August 2018 were collected, isolation of AB, antimicrobial susceptibility testing results, colonization of AB in lower respiratory tract (LRT), as well as diagnosis and treatment were retrospectively analyzed, efficacy of anti-AB infection treatment (treatment group) and non-anti-AB infection treatment (control group) in patients with AB LRTI were compared. Results A total of 106 strains of AB were isolated, 51.89% (55 strains) were colonized strains, healthcare-associated strains accounted for 43.40% (46 strains), 92.45% (98 strains) were isolated from LRT. Susceptibility rates of AB to 15 kinds of antimictrobial agents were all lower than 30%, susceptibility rates to polymyxin and tigecycline were 96.23% and 66.98% respectively. There were significant differences in white blood cell(WBC)/squamous cell, sputum culture, symptoms and signs of pneumonia, infection indicators and lung imaging between patients with AB colonization and LRTI (all P<0.05). Of 47 patients with AB LRTI, the total therapeutic effective rates were 88.00% in treatment group and 81.82% in control group, there was no significant difference in therapeutic efficacy between two groups of patients(P>0.05). Conclusion AB in general ICU mainly comes from LRT, most are colonized bacteria and can cause healthcare-associated infection, and only susceptible to polymyxin and tigecycline. LRT AB sputum smear, sputum culture, symptoms and signs of pneumonia, infection indicators and lung imaging are helpful to determine infection or colonization, clinical efficacy of treatment group is no better than that of control group.