Transesophapeal echocardiography (TEE) can be used as a diagnostic tool during cardiac surgery to direct the surgical procedure and diagnose unanticipated problems. TEE has also been one of the most important means of monitoring myocardial ischemia during coronary artery bypas grafting procedures. The cardiac anesthesiologist can apply intraoperative TEE in evaluating coronary artery anatomy and aorta atherosclerosis，assessing diastolic left ventricular function and preload，measuring intracardiac pressure and cardiac output，detecting ischaemic mitral regurgitation，intracardiac air and pericardial effusion.