Objective To explore the clinical features diagnosis and treatment of left main coronary artery (LM) disease. Methods According to the results of coronary angiography,significant stenosis was defined as ≥50% stenosis. Isolated LM group had 9 patients (4.62%),one-vessel stenosis LM group 15 patients (7.69%),two-vessel stenosis LM group 53 patients (27.18%) and three-vessel stenosis LM group 118 patients (60.51%). Results 195 cases (6.74%) of LM stenosis were found. The incidence rate was low. 164 patients (84.1%) had unstable angina,and 125 patients (64.1%) had myocardial infarction. Coronary artery bypass surgery was performed in 57 patients (29.2%) and the angina disappeared in most of them (84.2%). Five patients received unprotected LM stenosis and angina disappeared in all. Conclusion LM stenosis has sever symptoms. Coronary angiography is the only way for diagnosis and CABG the best treatment. Unprotected LM stenosis is valuable for some patients.