Oxygen saturation is the degree to which hemoglobin (Hb) binds oxygen, i.e., oxygen and Hb as a percentage of total oxygen-carrying Hb . Usually the normal value of oxygen saturation in a healthy person is 98% for arterial and 75% for venous. When the arterial oxygen saturation is 70%~89%, it may produce fatigue, drowsiness, unresponsiveness and other phenomena, which can be properly treated with oxygen; if the arterial oxygen saturation is less than 70, it is necessary to actively search for the cause of the disease, to avoid the harm caused by hypoxia. Usually the oxygen saturation on the monitor refers to the oxygen saturation in peripheral blood, which is mainly used to monitor whether the human body is hypoxic or not. The oxygen saturation on the monitor may have a certain degree of error, and if necessary, venous blood or arterial blood should be extracted to measure the oxygen saturation. If abnormal oxygen saturation is detected, please consult a doctor in time to avoid adverse consequences.