Pleural effusion (PE) is a complex etiology and affects the life quality life of patients.Invasive techniques play an important role in the diagnosis of PE.We mainly focus on the clinical application and evaluation of invasive techniques such as thoracocentesis, pleural biopsy and medical thoracoscopy in diagnosis of PE.Thoracocentesis is a simple, convenient and relatively safe technique with less complications which is often used as the initial diagnostic procedure.As pleural biopsy can provide pathological and histological specimens, its confirmed value is superior to conventional methods for diagnosis of PE.However, the positive rate is not satisfied and it can be improved when pleural biopsy is guided by ultrasound or computed tomography (CT). Pleural biopsy has great value in basic-level hospitals.Medical thoracoscopy can visually and clearly display almost whole of the pleura and lungs.Minor lesions and suspicious site can be showed for biopsy with medical thoracoscopy.As a result, the positive rate increases greatly and accordingly.In a word, medical thoracoscopy is a valuable and safe tool with a higher diagnostic rate and lower incidence of complications in clinic.