Double pneumonia is caused by the invasion of pathogens into the lungs. Pathogens are mainly seen in bacteria, viruses, fungi, as well as mycoplasma and chlamydia, which can induce pneumonia. The invasion of pathogens into the lung parenchyma leads to exudate in the alveolar cavity, which further triggers an inflammatory response and pneumonia, which is also greatly related to the patient’s weak immune system. The nature of pneumonia should be clarified as soon as possible by chest CT and other tests. Sputum culture, drug sensitivity tests, and routine blood and biochemical tests should be used to determine the pathogen and to provide the next rational treatment. For bacterial infections, a combination of sensitive antibiotics, phlegmolytics, and asthma medications can be considered.