Objective To investigate the diagnostic value of laparoendoscopic exploration and peri-toneum biopsy in patients with ascites of unknown origin and to study the feasibility of replacing hard laparo-endoscope with ultrathin gastroendoscope. Methods A total of 35 patients with ascites of unknown origin underwent laparoendoscopic exploration and biopsies were taken at suspected sites on peritoneum. Results Definite diagnosis was made in 33 patients after laparoendoscopy (94. 3% ), among which there were 10 tuberculosis peritonitis (28. 6% ), 7 metastatic peritoneal carcinoma (20%), 5 liver cancer, 3 liv-er cirrhosis, 3 primary peritoneal carcinoma, 2 ovary cancer, 1 hepatovascular sarcoma, 1 spleen lymphoma and 1 acidophilic enteritis. No procedure related complications were observed. Conclusion Laparoendosco-py is safe and effective in target peritoneal biopsy, and is of great importance in diagnosis of ascites of un-known origin.