Objective To explore the correlation between the expression level of interferon gamma(IFN-γ)and the severity of patients with septic shock and its prognostic value.Methods The clinical data and serum of 96 septic shock patients admitted to the Department of Critical Care Medicine,the First Affiliated Hospital of Guangxi Medical University from March 2022 to August 2023 were collected,and divided into survival group and death group according to the 28-day outcome;collected at the same time Sera from 30 healthy people undergoing physi-cal examination during the same period served as the control group.The enzyme-linked immunosorbent(ELISA)method was used to detect the expression levels of IFN-γ in the three groups,and the expression levels of IFN-γ and various clinical data between the groups were analyzed.Results The serum IFN-γ expression level of patients with septic shock was lower than that of healthy people undergoing physical examination,212.80(151.11,255.79)ng/L compared with 343.37(314.5,427.95)ng/L,P<0.01.Among the 96 cases of septic shock,There were 54 cases in the survival group and 42 cases in the death group.The clinical data of the two groups were com-pared.The gender,smoking history,SBP,DBP,SI,Lac,IL-6,IFN-γ,PCT,SOFA score,and APACHEⅡscore of the two groups of patients were compared.The difference is statistically significant(P<0.01).Logistic regression analysis showed that decreased expression of Lac,IFN-γ,and APACHEⅡ score were independent risk factors for death in patients with septic shock.[Odds ratio(OR)and 95%confidence interval(95%CI)were 6.491(1.404～30.004)respectively.0.954(0.954～0.999),3.476(1.210～9.984),P<0.05].The Spearman correlation analysis of INF-γ,Lac and APACHEⅡ showed a negative correlation,and the correlation coefficients were-0.38 and-0.35 respectively.Drawing the ROC curves of Lac,IFN-γ,and APACHEII,the AUCs of the three were 0.847,0.869,and 0.833 respectively.The AUC of the three joint predictions was 0.978.The joint prediction value of the three was better than that of a single indicator,P<0.001.Conclusion The decrease in IFN-γ expression level and the severity of septic shock patients have good prognostic value.