ABPM can provide 24 hours blood pressure informations for the patients. It can more accurately reflect patient's overall level of blood pressure, dynamic fluctuation and circadian rhythm change for 24 hours in a day and night. And it overcame the traditional measurement error and the 'white coat' effect, covered the shortage of casual blood pressure. For the clinical diagnosis of abnormal blood pressure, judgment of hypertension degree and evaluation of target-organ damage, it can guide rational antihypertension therapy, and provide more satisfactory method and scientific basis for making correct effect evaluation of anti-hypertensive drugs and doing clinical research. In genernal, it plays an important role in diagnosis, treatment and research of hypertension.