Abstract: According to the dfficult problem of the gas concentration easy over limit in the upper corner of the U type ventilation in the underground mine, an analyt ical method was applied to study on the air leakage field of the U type ventilation and the air flow filed caused by the pipeline gas drainage.In combination with the para meters of No.A504 coal mining face in No.2 Mine inclined shaft, the Fluent software was applied to the simulation of the gas control effect of the upper corner sealing 0 nly and the combined pipeline gas drainage in the upper corner sealing.The results showed that the gas control effect of the upper corner sealing was limited and the C ombined effect of the upper corner sealing and the pipeline gas drainage in the goaf would be the basic measure to control the gas concentration over limit in the upper corner of the U type ventilation.