1.Clinical characteristics: tuberculous pleural effusion occurs mostly under the age of 40, accounting for 2/3. The progression of the disease is slow and easy to control, and the pleural effusion is rapidly absorbed with proper treatment; cancerous pleural effusion mostly occurs above 40 years old (accounting for 2/3), generally without fever and continuous chest pain, sometimes hemoptysis, pleural effusion is medium to large amount, alkaline, 50% to 90% bloody, progresses fast and is not easy to control; 2.cytological examination: the positive rate of cytological examination of cancerous pleural effusion is 32% to 80%, and the false positive rate is 0.2% to 5%. 0.2%~5%, and false negative up to 41%. In order to improve the positive rate, the specimen should be large, fresh and repeatedly sent for examination. 3.Enzymatic examination: There are more biochemical tests for the differential diagnosis of tuberculous and cancerous pleural effusion, mainly ① adenosine deaminase (ADA): the sensitivity of ADA in diagnosing tuberculous pleural effusion is 100%, and the specificity is 97%; however, because typhoid fever, rheumatic fever, hepatitis, liver cirrhosis, hemolytic anemia and brucellosis can all cause elevated serum ADA, so in determining the significance of elevated serum ADA ② Carcinoembryonic antigen (CEA): CEA is significantly higher in malignant pleural fluid and ACE is not higher in tuberculous pleural fluid, which can be used to differentiate between the two. If CEA10μg/L is the boundary, the specificity of cancerous pleural fluid can reach more than 85%, pleural fluid CEA〉20μg/L, the specificity can reach 92%, if CEA〉55μg/L, the specificity can reach 98%. ③Lysozyme (LZM): LZM〉30μg/L in tuberculous pleural effusion, malignant pleural effusion generally does not have such inflammatory cells, LZM<30< span="">μg/L. 4.Bacteriological examination: As mentioned above, the positive rate of smear and culture are not high, PCR method to examine the tuberculosis bacilli in pleural fluid can improve the positive rate, but the maximum is only about 50%. 5.Pleural puncture biopsy: the positive rate of tuberculous pleurisy is 50%~80%, and the positive rate of pleural biopsy for cancerous pleurisy is 39~75%. 6, thoracoscopy and TV-assisted thoracoscopy: for cases that cannot be diagnosed by various methods for a long time, thoracoscopic biopsy, bacteriological examination and pathological examination have a confirmatory significance, and the positive rate of thoracoscopic biopsy can reach 98.4%. Television-assisted thoracoscopic technique (VATS) is a more mature technique developed in recent years, which can achieve the effect of previous open-chest biopsy with 85% sensitivity and 100% specificity. Various detection methods should be applied according to the principle of choosing the easy one before the difficult one.