The law of change of blood pressure every day is a double peak and double trough, a peak in the morning, a peak in the afternoon, and a minimum in the early morning. Normal blood pressure is a circadian rhythm, most people’s blood pressure in the morning between 6:00 to 10:00 this period appeared a peak, 4:00 to 8:00 p.m. when a peak, between the two peaks there is a trough, in the early morning between 2:00 to 3:00 there is a blood pressure between the lowest point. This phenomenon of double peaks and troughs is most pronounced in the elderly and hypertensive patients. The normal reference range for ambulatory blood pressure is currently considered to be a 24-hour average of less than 130/80 mmHg, a daytime blood pressure average of less than 135/85 mmHg, and a nighttime blood pressure average of less than 120/70 mmHg. According to the fluctuation law of blood pressure, the measurement of blood pressure should be chosen to be measured during the peak period of blood pressure, so that the measured blood pressure has a more guiding significance for the medication of hypertensive patients. However, in patients with long-term hypertension, the circadian rhythm of blood pressure will weaken or even disappear. When obvious hypertension occurs, it is necessary to actively consult the doctor and follow the doctor’s instructions for reasonable treatment.