To further explore the roadway cross-section variation under the condition of gas explosion propagation law differences, Fluent Numerical Simulation is used to simulate gas explosion propagation power characteristic mainly in two cases of the sudden narrowing of the roadway section and the gradual shrinkage of the roadway. The results showed that propagation velocity of explosive flame, which is suddenly reduced in roadway, is obviously higher than that in gradual shrinkage roadway. For the abrupt reduction of the cross section of the roadway, the peak overpressure of gas explosion shock wave instantaneously reaches its maximum value, in the roadway section of the mutation. For roadway section gradually decreasing, the peak overpressure of explosive blast wave increases with the propagation distance, but the amplitude of the explosion is still not great.