Abstract: Overpressure field of gas explosion in a confined roadway was studied via CFD software named AutoreaGas. The length of roadway is 25 meters with a section area size of 3 m×3 m. Shape and size of obstacles were simulated to obtain their influences on the overpressure caused by gas explosion, which confirmed the optimum blockage ratio corresponding to the peak value of overpressure. Based on the results obtained, the influence caused by gas concentration was also studied under optimum blockage ratio. All the simulation results show that the overpressure reaches a peak value and then falls down with the increases of blockage ratio as well as the gas concentration. And the optimum blockage ratio for this roadway is 26.6%, under which the overpressure reaches its peak value when the gas concentration is 9.5%.