Malignant pleural fluid needs to be specifically analyzed according to the severity of pleural fluid. If a small amount of pleural fluid is present, conservative treatment can be carried out; if it is a moderate or large amount of pleural fluid, thoracentesis is needed to drain the pleural fluid. 1. Small amount of pleural fluid: patients can be treated conservatively, mainly using furosemide diuretic drugs for treatment, patients such as combined with hypoproteinemia, need to supplement additional albumin treatment. 2. Medium or large amount of pleural fluid: patients can be treated with chest puncture to drain the pleural fluid, and at the same time, the specimen of the pleural fluid will be taken for laboratory examination to confirm the nature of the pleural fluid, and according to the pathological results, appropriate chemotherapeutic drugs or immunotherapy, radiotherapy, targeted therapy and so on will be selected. Malignant hydrothorax, need to find out the cause of malignant hydrothorax, need to target the primary cause of the treatment, usually patients have discomfort, timely to the hospital, do not be careless, so as not to delay the treatment.