The appearance of yellow sputum is not a symptom of a quick recovery. Most of them are more common in clinical practice when there is a direct presence of purulent bacterial infection that causes inflammatory reaction in the respiratory tract. For example, bronchitis, pneumonia, and even lung abscess caused by Staphylococcus aureus, Streptococcus pneumoniae, etc. In addition, it is also seen in the early stage of acute upper respiratory tract infection after being infected by a virus, due to the body’s resistance continues to decline, the inflammation does not completely subside, allowing purulent bacteria to take advantage of the situation and secondary infection, appearing with symptoms of coughing and coughing yellow sputum, indicating that the condition has worsened at this time. Clinically, we can check the blood routine, take X-ray or CT of both lungs, and take yellow sputum for pathogen culture and drug sensitivity test to clarify the condition, cause and treatment principle.