Abstract: After mining,the gas of 2560 coalface has been relatively stable(face gas concentration:0.15%,upper entry corner gas concentration: 0.55%,return air gas concentration:0.20%).With adjusting the ventilation system of 2560 coalface for safety retracement,but gas emission became abnormal after adjusting.The gas of down-corner angle had reached 8%,seriously affected the safety production.Through deeply analyzing the gas monitoring data,the surface atmospheric pressure monitoring data,the ventilation map of pre-and post ventilation system adjustment,the essential reasons for abnormal gas emission and corresponding measures were achieved,which ensure the safety retracement of 2560 coalface.