Intraoperative aortic dissection is a rare complication of open heart operations. Once dissection has occurred, great caution is required because of high mortality rate. We reported 4 cases of intraoperative aortic dissection. The incident rate was 0.08%, and the most common site of aortic injury was the aortic cannulation site( 3/4 patients). Intraoperative epiaortic echography is effective in diagnosis. All cases underwent graft replacement of the ascending aorta. The postoperative course was uneventful. Both prompt recognition and appropriate surgical management are mondatory to improve operative outcome.