Abstract: OBJECTIVE To investigate the clinical significance of high mobility group box 1（HMGB1） in evaluating the survival status of patients with hospital-acquired pneumonia（HAP） caused by multi-drug resistant Acinetobacter baumannii（MDRAB）. METHODS A total of 321 patients with HAP caused by MDRAB were admitted to the hospital between Jan. 2016 and Jan. 2020. According to the pneumonia severity index（PSI） at admission, the patients were divided into the low-risk group（n=90, PSI≤90）, the intermediate-risk group（n=109, 91 ≤PSI≤130） and the high-risk group（n=122, PSI＞130）. Serum HMGB1, procalcitonin（PCT） and tumor necrosis factor（TNF-α） levels among the three groups were compared. The relationship of the three indicators with PSI and prognosis was analyzed. The receiver operating characteristic（ROC） curve was plotted to evaluate the prognostic value of each index. RESULTS The severer condition the MDRAB HAP patients got, the higher serum HMGB1, PCT, and TNF-α levels（P＜0.05） were up-regulated. Spearman correlation analysis showed that the PSI score in patients with MDRAB induced HAP was positively correlated with serum HMGB1, PCT and TNF-α levels（P＜0.01）. After 28 days of clinical follow-up, 90 cases died and 231 cases survived. Serum HMGB1, PCT and TNF-α levels in the death group were significantly higher than those in the survival group（P＜0.05）. ROC curve analysis showed that 87.26 μg/L was the cut-off value, with the sensitivity of 83.33% and the specificity of 73.16%, and the area under the curve was 0.845, which were all better than those of PCT and TNF-α. CONCLUSION HMGB1, PCT and TNF-α are highly expressed in peripheral blood of patients with MDRAB induced HAP, and the expression of the three proteins is positively correlated with the severity of pneumonia. Detection of serum HMGB1, PCT and TNF-α levels in patients with MDRAB induced HAP can effectively assess disease progression and patient survival.