Abstract: In this paper, the source of low oxygen gas is analyzed with the background of 31406 working face of Jinjie Coal Mine, and the reasons for the decrease of oxygen concentration in the return air corner of the working face are studied. Results show that the cause of the working face with low oxygen is that the working face is in N₂-CO₂ zone; second, the low-temperature oxidation of the residual coal in the goaf leads to the high nitrogen and low oxygen content environment, and a large amount of low-oxygen gas flows through the air leakage channels from the goaf to the return air corner under the condition of negative pressure “U” type ventilation of the working face. Comprehensive prevention and control measures, such as plugging air leakage in goaf, enhancing intensity of airtight construction, removing anchor in triangular area of working face and strengthening monitoring and monitoring, are proposed to ensure the normal oxygen concentration of the working face at the return corner.