Abstract: In order to study the distribution law of gas in goaf and to determine the location of gas extraction roadway, taking 7433 working face of Kongzhuang Coal Mine as an example, based on the “O type circle” theory, adopting the method of partition assignment porosity, we carry out the numerical simulation on distribution of gas in goaf through the finite element analysis software COMSOL. The simulation results show that there is a dynamic equilibrium result between the leakage flow of the working face and the continuous discharge of gas; gas is enriched when 7433 working face advances to 180 m, which determines that the gas extraction roadway is in the crack zone, so the extraction effect is optimal when the inner alternated distance in the gas extraction roadway is within 10 m to 30 m range.