The most common opportunistic infection of AIDS is Pneumocystis carinii pneumonia. The clinical manifestations of patients are usually cough and chest tightness, some of which are accompanied by fever. Most patients have cough and sputum symptoms that are not very pronounced, but chest tightness symptoms will progressively worsen, and CT of the lungs is suggestive of interstitial changes in both lungs. Such patients need prompt treatment because of the risk of life-threatening respiratory failure. The most important treatment for Pneumocystis carinii pneumonia is the treatment of the pathogenic bacteria, and the drug of choice is SMZ. Of course, in severe cases, a combination of echinocandins is recommended. If the symptoms of chest tightness are more pronounced, hormones can also be used for symptomatic management.