Abstract: Objective To discuss the role of red blood cell distribution(RDW) in evaluating the prognosis of patients with sepsis caused by pulmonary infection. Methods Eighty patients with sepsis caused by pulmonary infection in the Affiliated Hospital of Hangzhou Normal University from January 2018 to December 2018 were retrospectively analyzed. They were divided into sepsis group and septic shock group according to the severity of the disease. The score of acute physiology and chronic health evaluation Ⅱ(APACHE Ⅱ) and RDW of the two groups were compared, the Pearson correlation coefficient is used to measure the strength of a linear association between between APACHE Ⅱ score and RDW. Multivariate logistic regression model was used to analyze the independent risk factors affecting the prognosis of sepsis. ROC curve was used to analyze the predictive value. Results APACHE Ⅱ score and RDW in the septic shock group were significantly higher than those in sepsis group(all P<0.05). There was a significant positive correlation between RDW and APACHE Ⅱ score(r=0.015, P<0.001). Logistic regression analysis of multiple prognostic factors in patients with sepsis showed that the levels of APACHE Ⅱ, SOFA, PCT and RDW were all important risk factors affecting the prognosis of patients with sepsis. The ROC curves of PCT, APACHE Ⅱ, SOFA and RDW to predict the prognosis of septic patients showed that the AUC of these four indexes were 0.922, 0.878, 0.888 and 0.935, respectively, and there was no significant difference among APACHE Ⅱ score, SOFA score and AUC of PCT(all P>0.05). The critical value of RDW diagnosis was 14.92% the critical value of APACHE Ⅱ score was 16 points, the critical value of SOFA score diagnosis was 6 points, and the critical value of PCT diagnosis was 24.02 ng/mL. Conclusion The higher the level of RDW, the more serious the sepsis condition, and the worse the prognosis of patients, which has certain evaluation value for the prognosis of sepsis patients.