In today’s society, the incidence of hypertension is increasing year by year and has gradually become a common chronic disease in China. At present, the diagnosis of hypertension still utilizes the measurement of blood pressure in the upper arm clinic as its basis. However, there are some patients who have high blood pressure when they see the doctor, or have high blood pressure at night and normal blood pressure during the day, and the blood pressure in the outpatient clinic can not reflect the patient’s overall blood pressure status and 24h dynamic changes. Therefore, 24h dynamic blood pressure examination becomes a better means. So which groups of people are suitable for this examination? 1, white coat hypertension. Some patients and friends just found high blood pressure because of physical examination, measured blood pressure in outpatient clinic in 140-179/90-109 mmHg within the range of 1,2 hypertension, and measured blood pressure at home <135/85 mmHg, usually need to carry out 24 h ambulatory blood pressure monitoring, in order to exclude the white coat hypertension. 2.Nighttime hypertension. Nighttime is the time when the body's resistance is the weakest in a day, and a part of people's blood pressure rises at night, which often becomes the trigger of some nocturnal cerebral infarction or heart attack. 3.Nighttime low blood pressure. At night the human body metabolism slows down, normal blood pressure at night around 3 o'clock when asleep blood pressure is lowest, there are some due to neural regulation disorders caused by hypertension patients friends, blood pressure day and night difference is larger, the night is easy to cause low blood pressure, low blood pressure for a long time will cause insufficient cerebral perfusion, but also cause cardiovascular and cerebrovascular pathologies. Concealed hypertension, this type of blood pressure is "invisible", the patient will come to outpatient clinic because of "dizziness" and other discomforts, but in the clinic for many times to measure the blood pressure is normal, at this time we have to suggest him to do dynamic blood pressure to observe whether there is a rise in blood pressure. This time, we should suggest him to have an ambulatory blood pressure (BP) test to see if his BP is rising. Evaluate the effect of antihypertensive drugs. Patients who have been taking antihypertensive drugs for a period of time, how effective they are, whether their blood pressure drops too low at night or fluctuates too much because of the medication, all of these need to be evaluated by 24h ambulatory blood pressure, and the doctor will use the results to adjust the medication for the patient.