Abstract: Objective: To explore the change trend of serum total antioxidant capacity (TAC) levels within 7 days after the onset of sepsis and its relationship with the risk of in-hospital death within 28 days.Methods: A total of 167 patients with sepsis admitted to the Affiliated Hospital of Qinghai University from March 2016 to March 2021 were enrolled and divided into survival group and death group according to 28-day survival.Sequential organ failure assessment (SOFA) score, and serum, lactic acid, malondialdehyde (MDA) and TAC levels on day 1, 3 and 7 after onset of sepsis were compared between the two groups.Pearson correlation analysis was used to test the correlation between serum TAC levels and clinical characteristic parameters.Multivariate logistic regression model was used to analyze the risk factors of 28-day in-hospital death in sepsis patients, and receiver operating characteristic (ROC) curve was used to evaluate the clinical value of serum TAC levels in predicting the risk of in-hospital death within 28 days.Results: The serum TAC levels in death group were higher than those in survival group on day 1, 3 and 7 after onset of sepsis (P＜0.05).The levels of serum TAC were positively correlated with the scores of lactic acid, MDA and SOFA on day 1, 3 and 7 after onset of disease(P＜0.05).Multivariate logistic regression analysis showed that serum TAC levels on day 1, 3 and 7 after onset of disease were all independent predictors of 28-day in-hospital death in patients with sepsis (P＜0.05), and their areas under ROC curve (AUC) for predicting in-hospital death of sepsis patients within 28 days were 0.629 (95% CI:0.542-0.716), 0.593 (95% CI: 0.500-0.687) and 0.745(95% CI:0.669-0.820), respectively.Conclusion: The serum TAC levels of septic dead patients within 7 days after onset are continuously higher than those of surviving patients, and it is related to the aggravation of sepsis and the increase of death, which can be used as a prognostic biomarker of sepsis.