Abstract: Abstract Objective：To study the guidance value of gas in pleural cavity partial pressure evaluate twice of pneumothorax and arterial blood gas analysis in patients with blocked drainage tube for further treatment. Methods: The patients with intercostal tube and water seal bottle percutaneous drainage, but drainage tube blocking and ipsilateral lung is not reexpansion. Extracted gas in the pleural cavity twice, do gas partial pressure evaluate and arterial blood gas analysis of radial artery. In accordance with [Pp（CO2）], [Pp（O2）], [Pp（CO2）] / [Pp（O2）]，[Pp（CO2）]and[p（CO2）judge different type of pneumothorax in patients with the blocked drainage tube, choose the way to treatment. Result: The group of 49 patients, 30 cases judged closed pneumothorax, 16 cases of traffic pneumothorax , 3 cases of tension pneumothorax; coincidence rate is 97.96%(48/49). Including tension pneumothorax and traffic pneumothorax are 100%，closed pneumothorax is 96.67%（29/30），97.96%（48/49）patients get a scientific treatment. Conclusion: To extract the gas of pleural cavity and evaluated twice, according to the results determine the type of patients with pneumothorax is more accurately, the exhaust in order to take a scientific and effective measures.

Key words: spontaneous pneumothorax, drainage, gas partial pressure evaluate