Abstract: Objective: To explore the risk factors and interaction effect of postoperative delirium in patients with cardiopulmonary bypass heart valve replacement.Methods: A total of 358 patients with cardiopulmonary bypass heart valve replacement admitted to the Department of Cardiovascular Surgery of Guangxi Zhuang Autonomous Region People's Hospital from January 2019 to June 2022 were selected and divided into delirium group (n=92)and non-delirium group (n=266).Logistic regression was used to analyze the risk factors of postoperative deliri-um in patients with cardiopulmonary bypass heart valve replacement.Multifactor dimension reduction (MDR)was used to analyze the interactions among risk factors.Receiver operating characteristic curve (ROC) was drawn to evaluate the sensitivity and specificity of the model.Results: There were statistically significant differ-ences in age, diabetes, postoperative use of sedatives, duration of mechanical ventilation, duration of cardiopul-monary bypass and block duration between the two groups (P< 0.05).The use of postoperative sedatives, diabe-tes and the duration of cardiopulmonary bypass had an significant interaction effect (P< 0.05).The area under ROC curve (AUC) of the regression model with interaction effect was 0.859 (95% CI: 0.815-0.903), the optimal cut-off value was 0.267, the specificity was 0.744, and the sensitivity was 0.739.The AUC of the model without adjustment for interaction effect was 0.851(95%CI:0.806-0.895), the optimal cut-off value was 0.266, the speci-ficity was 0.759, and the sensitivity was 0.761.Conclusion: Age, postoperative use of sedatives, duration of me-chanical ventilation, duration of cardiopulmonary bypass and block duration are all risk factors for delirium.The interaction effect of postoperative use of sedatives, diabetes and duration of cardiopulmonary bypass may be im-portant predictors for postoperative delirium.