The differentiation of community-acquired pneumonia mainly includes tuberculosis, lung cancer and pulmonary thromboembolism. 1. Tuberculosis: most of the patients have symptoms of generalized toxicity such as low afternoon fever, night sweating (abnormal sweating after going to sleep, and sweating stops after waking up), emaciation, and fatigue, and chest radiographs or CT of lungs show that most of the lesions are in the upper lobe or dorsal segment of lower lobe of lungs, and Mycobacterium tuberculosis can be found in the sputum. 2. Lung cancer: most of the patients do not have acute toxic symptoms of infection, sometimes there can be irritating cough, sputum, chest pain, blood in sputum and so on. Combined with lung CT, bronchoscopy biopsy and other examinations can help to identify. 3. Pulmonary thromboembolism: patients may have symptoms such as dyspnea, shortness of breath, chest pain, etc., and hypoxemia and acidosis may appear in blood gas analysis, and D-dimer, CT pulmonary arteriography and radionuclide scanning can help to identify it. In addition, it also needs to be identified with pulmonary edema, interstitial lung disease and other diseases, patients with respiratory symptoms, it is recommended that timely medical care, improve the relevant laboratory tests to clarify the diagnosis, and then give targeted treatment.