Objective：To investigate the correlation between mean platelet volume(MPV) and abnormal drainage induced by postoperative anticoagulant therapy in patients undergoing coronary artery bypass grafting with valve replacement，to provide evidences for formulating postoperative anticoagulant treatment regimens. Methods：Retrospective analysis was performed on 72 patients received coronary artery bypass grafting with concomitant valve replacement.The patients were divided into 2 groups by P75 of the total drainage volume and the anticoagulation-related bleeding. Results：Preoperative MPV presented a negative correlation with preoperative platelet count(r=-0.511，P＜0.001)，and a positive correlation with postoperative drainage volume(r=0.300，P=0.013).In Group 2，patient’s age，proportion of patients with history of alcohol intake，using biovalve and postoperative platelet transfusion volume were all higher than those in Group 1，the preoperative MPVe was higher than that in Group 1，and the postoperative platelet count was lower than that in Group 1(all P＜0.05).Age，history of alcohol intake，and preoperative MPV were shown to be independent risk factors for postoperative abnormal drainage.When plotting the receiver operating characteristic(ROC) curve for MPV，the area under the curve(AUC) was 0.691(95%CI 0.553~0.829，P=0.012)，the optimal cut-off point was 10.75 fl，the sensitivity was 0.714，and the specificity was 0.617. Conclusion：In patients undergoing coronary artery bypass grafting with valve replacement，preoperative MPV presented significant correlation with abnormal drainage induced by postoperative anticoagulant therapy，indicating its good predictive value.For those patients with the preoperative MPV＞10.75 fl，older age，history of alcohol intake，and received biovalve replacement， exercise in postoperative anticoagulation should be careful，and attention should be paid to monitoring of coagulation function.