The four stages of lobar pneumonia are: congestion and edema stage, red hepatoidosis stage, gray hepatoidosis stage, and dissolution and dissipation stage. 1. Congestive edema stage: on the 1st to 2nd day of the disease, it is mainly characterized by plasma inflammation. Patients may have chills, high fever, cough, sputum symptoms, due to the alveoli filled with plasma exudate, so the patient cough thin sputum. Clinical examination reveals wet rales, elevated white blood cell counts, and a chest X-ray that shows flaky, fuzzy shadows. 2. Red hepatoid phase: usually on the 3rd to 4th day after the onset of the disease, with the progress of the disease, the patient may appear chest tightness, cyanosis and other symptoms of hypoxia, due to the alveoli filled with red blood cells, so the patient’s sputum is rust-colored. Wet rhonchi can be heard on lung auscultation, Streptococcus pneumoniae can be detected on sputum examination, and chest X-ray shows a large dense shadow. 3. Gray hepatoid phase: generally after the onset of the disease, on the 5th to 6th day, the patient still has fever, cough, sputum and other symptoms, due to the reduction of erythrocytes in the alveoli, increase in cellulose, the patient coughed up rust-colored sputum gradually changed into mucopurulent sputum. Wet rhonchi can be heard in clinical examination, and chest X-ray shows a large dense shadow. 4. Dissolving and dissipating period: about one week after the onset of the disease, the patient’s body temperature gradually decreases, the symptoms and signs gradually reduce and disappear, and the chest X-ray gradually returns to normal. The duration of lobar pneumonia is about 1~2 weeks, and it is recommended to consult the doctor whenever discomfort occurs.