Symptoms will appear after quitting smoking, such as spitting yellow sputum, which is a very good phenomenon after quitting smoking, because after tobacco is inhaled into the respiratory tract by the human body for a long time, harmful components, including tar and nicotine, will damage the mucous membrane of the respiratory system, often leading to chronic inflammation of the airways, and inflammatory secretions of the airway mucous membrane will be exuded, such as chronic bronchitis. After quitting smoking, the mucous membrane of the lungs is no longer damaged by tobacco, and the mucous membrane of the lungs will activate the immune system, which will continuously expel the inflammatory secretions produced in the lungs, so it will show yellow sputum discharge, which is the process of self-repair of the human lungs after quitting smoking.