The presence of clear jelly-like sputum is not necessarily a sign of lung cancer and should be determined on a case-by-case basis. Sputum is the fluid secreted by the irritated respiratory tract. If clear jelly-like sputum appears, the most common causes are Klebsiella infection and chronic pharyngitis. In addition to clear jelly-like sputum, Klebsiella infection may be accompanied by chills, high fever, chest pain, and even diarrhea and jaundice; chronic pharyngitis may present with throat discomfort, dryness, irritating cough, and foreign body sensation. However, it is true that lung cancer patients are also prone to cough and sputum, and the sputum may also appear transparent jelly-like, and in severe cases, blood in sputum or hemoptysis may occur. Therefore, clear jelly-like sputum is not necessarily lung cancer and does not have diagnostic significance. Patients with clear jelly-like sputum should go to the respiratory department or related departments of the hospital in time for clear diagnosis and symptomatic treatment.