Human blood pressure fluctuates on a daily basis. Recognizing the law of blood pressure fluctuation and change is very meaningful for the prevention and treatment of hypertension. First, the factors affecting blood pressure blood pressure is arterial blood pressure, refers to the flow of blood to the side of the blood vessel wall pressure, is the result of the interaction of the two forces of the heart ejection and peripheral resistance. Blood pressure has a systolic and diastolic pressure, when the heart contraction period, arterial blood pressure rises to the highest value, called systolic pressure; when the heart diastolic period, arterial blood pressure falls to the lowest value, called diastolic pressure. Mercury column sphygmomanometers are commonly used, as well as metered sphygmomanometers and electronic sphygmomanometers to measure blood pressure. Blood pressure is in dynamic equilibrium, emotions, environment, diet, warm and cold, as well as the measurement method and other factors, may affect the rise and fall of blood pressure, drinking, smoking, pain, anxiety, exercise, 1, half an hour before measuring blood pressure do not drink alcohol, do not drink strong tea with non-smoking, calm, empty the urine and stool, no longer eat. 2, calm rest for 15 minutes before measuring blood pressure. 3, the blood pressure monitor should be at the same level with the heart. 4. Avoid compression of the arm by the sleeve. Maintain proper tightness between the air sleeve of the sphygmomanometer and the anterior lateral arm artery. 5. The gas in the air sleeve of the sphygmomanometer should be completely discharged. Second, there are two peak periods of daily blood pressure Most people have an obvious circadian rhythm of blood pressure, that is, the blood pressure is higher during the daytime activities and lower at night after sleep. Generally there are two peak periods of blood pressure during the day, i.e. 6-10 am and 4-8 pm. Therefore, blood pressure is measured during these two hours to get an idea of the highest point of blood pressure during the day. The highest blood pressure value throughout the day is mostly in these two periods, and then gradually decreases to 1 to 2 a.m. for the lowest blood pressure value throughout the day, that is, the second trough, and finally gradually rises again into the first peak of the next day. The difference between high blood pressure day and low blood pressure night is related to the human biological clock, and is also the result of the comprehensive regulation of the body’s nerves, body fluids, endocrine and so on. Whenever the human biological clock changes, the blood pressure will also change, for example, nurses, workers and duty personnel working on night shifts may have their peak blood pressure in the evening every day. Third, the significance of the application of blood pressure peak hours.1, to understand the value of a person’s blood pressure, it is necessary to choose to measure at two peak hours in order to reflect the blood pressure of the body.2, to be measured three times in a row during the peak hours of blood pressure, to take its average, when the systolic blood pressure ≥ 140 mmHg or diastolic blood pressure ≥ 90 mmHg, before the diagnosis of hypertension; leave the peak hours of blood pressure measurement, there may be missed hypertension diagnosis.3. Blood pressure should be measured at the same peak hour of the day to compare the blood pressure. If blood pressure is measured in the morning on one day and in the afternoon on another day, it is difficult to compare blood pressure levels. 4. Use blood pressure-lowering drugs before the peak hours to grasp the antihypertensive effect of short-acting, medium-acting and long-acting preparations. If a patient with hypertension has poor results with medication, it is important to find the cause of the elevated blood pressure, whether there are complications of hypertension, and whether the medication used is right. In addition, it is necessary to find out the daily blood pressure peak hours, find out the pattern of blood pressure changes, and take the appropriate treatment.