The full name of blood gas refers to arterial blood gas analysis, in which arterial blood is drawn and tested to observe the three main indicators. 1. pH, or acidity and alkalinity, has a normal range of 7.35-7.45, with a median value of 7.4. If it is low, acidosis is considered, and if it is high, alkalosis is considered. 2. The normal value of oxygen partial pressure is between 80-100mmHg, greater than 60mmHg is hypoxemia, less than 60mmHg is considered type I respiratory failure. 3, we need to look at the bicarbonate, which represents the concentration of alkali, the bicarbonate value is significantly lower, we should consider the possibility of acidosis; bicarbonate value is significantly higher, we should consider the possibility of alkalosis, as to whether it is respiratory alkalosis or metabolic alkalosis, we need to refer to the specific disease. If the patient is a respiratory disease, consider respiratory acid-base balance disorder mainly; if it is a nephrotic metabolic disease, consider metabolic disease, mainly primary and the rest secondary. Therefore, the normal value of blood gas analysis enables the differential diagnosis of the combination of oxygen and carbon dioxide metabolism in respiratory diseases, so that clinicians can give targeted treatment.