Objective To analyze related factors affecting the prognosis of patients with Acinetobacter baumannii (A.baumannii)bloodstream infection(BSI),guide clinical prevention and treatment.Methods A case-control study was conducted to retrospectively analyze patients with A.baumannii BSI in Peking University Third Hospital from January 2012 to December 2016.According to prognosis,patients were dividedinto poor prognosis group and good prognosis group. Univariate analysis and logistic regression analysis were used to analyze the risk factors of poor prognosis in patients with A.baumannii BSI.Results There were 58 confirmed cases of A.baumannii BSI,including 31 patients with poor prognosis and 27 with good prognosis. Univariate analysis revealed that risk factors for poor prognosis of A.baumannii BSI were antimicrobial use and at least two kinds of antimicrobial agent use three months before admission,at least two kinds of antimicrobial use,and carbapenems use before infection after admission,increase of white blood cell(WBC)count after infection(P<0.05). After 3-day anti-infective treat-ment,examination results of WBC count and X-ray chest film in good prognosis group were all better than poor prognosis group(P<0.05). Logistic multivariate regression analysis showed that independent risk factors for poor prognosis of A.bau m annii BSI were antimicrobial use three months before admission,at least three kinds of antimicrobial use and carbapenem use before infection after admission,increase of WBC count and WBC count>12×109/L after infec-tion,as well as increase of WBC count and WBC count>15×109/L after 3-day anti-infective treatment(P<0.05). Conclusion The probability of poor prognosis is high in patients with A.baumannii infection. For patients receiv-ing≥2 kinds of antimicrobial agents three months before admission,patients receiving≥3 kinds of antimicrobial agents as well as patients receiving carbapenems before infection after admission,the likelihood of A.baumannii BSI should be paid attention.For patients with WBC count>12×109/L after infection and WBC count>15×109/L after 3-day treatment,poor prognosis should be alerted,treatment plan needs to be adjusted in time to reduce the mortality.