If the pleural effusion has not been drained, it is often considered that the primary disease is not well controlled, such as tuberculosis, or carcinomatous pleural fluid. Clinically, pleural effusion refers to the excessive accumulation of fluid in the pleural cavity, and common causes include tuberculosis infection, bacterial infection, malignant tumors and so on. Infections such as Mycobacterium tuberculosis or pleural metastasis of cancer cells lead to an increase in the permeability of the pleural blood vessels, and the water in the blood vessels penetrates into the pleural cavity causing pleural effusion. Whether pleural effusion is curable or not is closely related to the cause of the disease, and if the cause of the disease is eliminated, pleural effusion can be absorbed by the body. Except for the pleural fluid caused by malignant tumors, such as tuberculosis, common bacterial infections, standardized treatment can basically be cured. If the fluid is not drained all the time, it should be considered whether the tuberculosis bacillus or bacterial infection is not well controlled. Cancer pleural fluid, due to the cause of the disease is difficult to eliminate, and there is a progressive deterioration of the possibility, can be injected into the pleural cavity of the relevant drug treatment to reduce the symptoms, but it is difficult to completely remove. In conclusion, it is recommended that patients with pleural effusion seek timely medical attention to avoid delaying their condition.