Pulmonary effusion, also known medically as pleural effusion. Pleural effusion can have a long or short course, and some patients may not be able to sleep flat and need to be semi-recumbent or sit up to be more comfortable. The first step is to treat the cause and, if necessary, to release the fluid from the chest to relieve the symptoms. If pleural effusion occurs, the cause needs to be identified first to determine if it is inflammation, infection, trauma, and systemic diseases including hypoproteinemia, etc. Then symptomatic treatment should be given according to the cause, and if necessary, fluid should be aspirated or a closed chest drain should be placed to relieve the symptoms. Be careful not to exceed 700 ml of fluid for the first time and 1000 ml each time thereafter, otherwise it may lead to acute pulmonary edema and other critical conditions. Also send the pleural effusion fluid for relevant examination before follow-up examination and treatment. Traumatic pleural effusion requires good timing and, if necessary, emergency open-chest exploration and surgical treatment in order to save the patient’s life. Therefore, the treatment of pulmonary effusion, i.e. pleural effusion, needs to be based on the patient’s specific situation, firstly to clarify the cause, then to follow up with the necessary treatment according to the cause, and if necessary to perform thoracentesis and drainage or emergency surgical exploration to stop the bleeding and save the patient’s life.