The pressure generated by the flow of blood in the vessels on the vascular wall is called blood pressure. Blood pressure is one of the important vital signs of human body, and it has very important clinical significance. The sphygmomanometer is an instrument for measuring blood flow pressure. According to the detection method, it can be divided into three categories: mercury column sphygmomanometer, aneroid sphygmomanometer and electronic sphygmomanometer. Among them, the mercury column sphygmomanometer has the highest accuracy and stability.