A small amount of pleural effusion after breast surgery may be related to lung inflammation and infection, malignant tumor, etc. Drug therapy, thoracentesis and fluid extraction can be carried out according to the cause of the disease. 1. Drug treatment: when there is a small amount of pleural effusion, after clarifying the cause of the effusion, corresponding treatment will be taken, such as hydrothorax caused by malignant tumor breast cancer, antitumor drugs such as cyclophosphamide and other treatments are feasible; if it is tuberculous hydrothorax, anti-tuberculosis drugs such as rifampicin and other treatments are feasible; if it is hydrothorax caused by pneumonic infections, anti-infectives such as ceftriaxone and other antibiotics are feasible to carry out the treatment. 2. Thoracentesis and fluid extraction: when there is a small amount of pleural effusion, the effusion can be directly extracted and discharged by thoracentesis. If the fluid is not well localized, it can be punctured under ultrasound localization. It is recommended that patients go to regular hospitals in a timely manner to identify the causes and receive treatment as prescribed by the doctor, so as not to delay the condition.