Abstract: After a long time evolution, there will be gas in the old empty lane with a certain concentration and pressure. The gas emission will happen when exposing empty lane in the process of residual coal repeated mining of heading face.1202 heading face is taken as research background in Shenghua Coal Industry. Through the fluid dynamics software Fluent, gas concentration variation and distribution law is simulated in working face and empty lane when empty lane is exposed for roadway excavation. The results show that the gas concentration increases rapidly in heading face at first, then decreases rapidly, it decreases under 1% about 3 min later, with the ventilation time lengthened, the gas concentration is close to zero. At the same time, the gas concentration in two ends of empty lane increases rapidly firstly, then decreases rapidly, it decreases under 1% about 3 min later, as the ventilation time going, the gas concentration is close to zero too.