Blood pressure measurement by cell phone is not very accurate, and there is no authoritative data to report how much error there is. The principle of blood pressure measurement by cell phone is to assess blood pressure indirectly based on pulse wave and pulse rate, and there is an error with the real blood pressure of human body, which can’t be used as a standard for diagnosis and monitoring of blood pressure, and there is no authoritative data to report how much the error is with the real blood pressure. Therefore, blood pressure measurement by cell phone is not accurate. The most accurate way to measure blood pressure is to monitor it with a sphygmomanometer with a mercury column. Next, there are electronic sphygmomanometers. Among the electronic sphygmomanometers, this kind of sphygmomanometer at the wrist has the worst measurement effect, while the electronic sphygmomanometers that measure above the elbow have a relatively higher accuracy rate. Measurement of blood pressure needs to be in a quiet environment to sit still and rest for 10-15 minutes before starting to measure, in the process of measurement, to prevent themselves from nervousness and other emotions, only in this way can we obtain a normal or accurate blood pressure value.