Normally there is only 10-30 ml of pleural fluid in the pleural cavity, which plays a lubricating role. Pleural effusion due to malignant tumor invading the pleura or malignant tumor metastasizing to the pleura thus resulting in pleural effusion is called malignant pleural effusion or malignant pleural fluid. Malignant pleural effusion is a commonly encountered clinical problem, and the most common cause is lung cancer, others include breast cancer, lymphoma, ovarian cancer, etc. The incidence of lung cancer has been increasing in recent years, and malignant pleural fluid caused by lung cancer has become more and more common in clinical practice. Malignant pleural fluid often grows rapidly and is difficult to control, and patients often suffer from chest tightness, shortness of breath or even difficulty in breathing, resulting in a serious decline in patients’ quality of life. According to the latest international lung cancer staging, regardless of the size of lung cancer, as long as malignant pleural fluid appears, it is stage V, i.e. advanced lung cancer, which is generally considered to have lost the indications for surgery and can only be treated by non-surgical methods. However, malignant pleural fluid reduces the efficacy of radiotherapy, while the large amount of pleural fluid causes respiratory distress and makes it difficult for patients to tolerate chemotherapy, which greatly limits clinical treatment. The first task of malignant pleural fluid treatment is to control the pleural fluid. Repeated pumping of pleural fluid is not a good treatment method, and the effect is not long-lasting, which will lead to a large loss of body fluid and protein in addition to bringing pain to patients. Injecting or spraying “adhesives” into the chest cavity to make the lung and chest wall extensively adhere and eliminate the free chest cavity is a method often applied in clinical practice, which can control the pleural fluid in most patients but has no therapeutic effect on the metastatic cancer of the pleura. Theoretically, the most ideal method is to control malignant pleural fluid and at the same time provide some treatment for metastatic cancer in the pleura, such as reducing tumor load by removing metastatic cancer in the pleura and combining with hot irrigation chemotherapy (hot irrigation chemotherapy is to add chemotherapeutic drugs to hot water at 42℃ to continuously circulate and irrigate the chest cavity, in addition to directly killing the tumor, heat therapy can also promote the absorption of chemotherapeutic drugs in the tissue, and the drugs can penetrate into the tissue for several millimeters), which can also satisfactorily control malignant pleural fluid. (mm), which can also satisfactorily control the pleural fluid. According to patient’s specific conditions, we can consider different treatment strategies: 1.Lung cancer combined with pleural effusion, but no tumor cells are found in the preoperative pleural fluid, according to the standard lung cancer surgery preparation, thoracoscopy carefully explores the chest cavity before lung resection, and lung lobectomy (small tumor can also be lung segment or local resection), lymph node dissection and thoracic heat irrigation chemotherapy are performed if no clear pleural tumor metastasis is seen. 2.Lung cancer combined with malignant pleural fluid, small peripheral lung cancer with cancer cells found in the preoperative pleural fluid, local resection of tumor under thoracoscopy, resection of pleural metastases and chemotherapy with hot irrigation of the pleural cavity, and specimens sent for relevant molecular markers and gene detection. 3.Patients with lung cancer combined with malignant pleural fluid and cancer cells found in the preoperative pleural fluid that are not suitable for surgery can consider taking pleural fluid for tumor-related molecular markers and gene detection, hot irrigation chemotherapy or intrathoracic spraying of talcum powder or injection of “adhesion agent” through the chest tube to promote thoracic adhesion. After control of the pleural fluid, the patient’s condition will be re-evaluated and the next chemotherapy or radiotherapy plan will be decided.