Coronary artery stenosis 40 is usually defined as 40%, which is a more dangerous level and should be actively treated. Usually after coronary atherosclerosis, the lumen of the coronary artery will be narrowed or occluded, which makes the imbalance between the blood supply of the coronary artery and the blood demand of the myocardium, resulting in the blood flow of the coronary artery not being able to satisfy the basic demand of the myocardium’s metabolism, and therefore causing the symptoms of myocardial ischemia and hypoxia, which leads to the symptoms of chest tightness, chest pain and other uncomfortable symptoms. In order to clarify the degree of coronary artery stenosis, coronary angiography is required. A guide wire is inserted into the coronary artery through the radial artery or femoral artery, and a contrast medium is inserted for examination. If the examination result suggests that the degree of stenosis is 40%, although it does not meet the indication for stent placement, it will affect the blood supply to the heart and may cause discomfort such as chest tightness and chest pain after physical labor or emotional excitement. If left untreated, it will lead to its further narrowing and discomfort such as acute myocardial infarction. In daily life, we should eat a light diet, can follow the doctor’s advice to choose metoprolol to reduce myocardial oxygen consumption, nitroglycerin to reduce myocardial oxygen demand and improve myocardial perfusion, nifedipine can reduce myocardial oxygen, consume expansion of the coronary artery, improve myocardial blood supply, and so on. If the coronary artery stenosis 40% need to pay attention to observation, follow the doctor’s instructions to take drugs. Any uncomfortable symptoms, you should immediately consult a doctor for treatment.