Pleural disease is a common disease of the respiratory system, and pleural effusion is the most common manifestation of pleural disease, which is difficult to diagnose due to the diversity of etiologies. For large amount of pleural effusion of unknown cause, clinical diagnosis is mostly made by routine pleural effusion, biochemical, microbiological and cytological laboratory tests, combined with percutaneous pleural biopsy, but still 10% ~ 27% of pleural effusion is difficult to define the cause. As an invasive examination, thoracoscopy has the advantages of simple operation, clear observation field and safety, which can significantly improve the positive diagnosis rate of pleural effusion. Because the pleura can be explored more comprehensively during thoracoscopy, not only can the lesion be directly visualized, but also multi-site biopsy can be performed, which obviously improves the positive rate of pleural disease diagnosis. Therefore, the application of this technique is of great value for the diagnosis of pulmonary pleural diseases.