Abstract: In order to study the effect of different depth of cannula in upper corner on gas drainage, FLUENT is used to simulate the gas distribution of working face and goaf without gas drainage and under the condition of 1 m, 3 m, 5 m cannula depth at the background of 104 working face in Dangjiahe Coal Mine. Numerical simulation results show that the deeper of the cannula is, the lower gas concentration of the upper corner is. But the gas drainage of cannula can hardly influence the gas distribution of the other area except for the upper corner. Apply the research results into practice, measured data show that gas concentration of the upper corner of 104 working face is lower than 0.7%. Study shows that gas drainage of cannula can extract gas of upper corner effectively, the gas concentration of upper corner is effectively controlled at the same time.