Coughing is a defensive reflex and a symptom and reflection of disease. Coughing with cyan-colored sputum mostly indicates the presence of infection, which may be both bacterial and viral. The majority of them are self-limiting and can be cured naturally in about 7 days or with antibiotics. 2. Acute bronchitis can also appear as cough with cyan sputum and can be cured in about 7 days after anti-infection treatment. 3. Bronchiectasis, Pseudomonas aeruginosa infection can appear as cyan sputum or green sputum and often requires hospitalization with infusion therapy. 4, Pneumonia, lung abscess and other diseases can also appear coughing and coughing up cyan-colored sputum, so it is necessary to specify the cause and take targeted treatment.