Abstract: To investigate the bidirectional propagation law and inhibition effect of gas explosions, experimental studies were conducted on a self-built explosion pipeline platform. The horizontal pipeline system was composed of three transparent acrylic glass sections each with a length of 1 m. In the experiments, each section was filled with methane/air mixtures of different volume fractions, ignition was initiated at a position slightly to the right of the center, and the explosion flame propagated to both sides. One piece of porous medium was placed in each of the left and right pipelines to observe the influence of porous media with different pore densities on explosion propagation. The flame images, propagation velocity and explosion overpressure during the explosion process were all analyzed. The results show that porous medium with a pore density of 10 ppi (1 ppi=39.37 pores per meter) exerts an excitation effect on the flame (accelerates its propagation), while porous media with pore densities of 20 ppi and 30 ppi produce an inhibition effect on the flame. With ignition at the position slightly to the right of the center, the flame reaches the porous medium on the right first, and the excitation or inhibition effect of the right porous medium on flame propagation is more significant than that of the left one at this time. Under the combined action of methane volume fraction difference and porous media, the flame velocity curves for propagation from the center to the left and right present a combined W-shape, meaning the velocities of the flame fronts propagating leftward and rightward all undergo a slow growth stage, a downward fluctuation stage and a rapid rise stage. The variation in pore density of the left porous medium has a negligible effect on the rightward propagation of the explosion flame (with the same pore density of the right porous medium, the time for the flame to propagate to the right end of the pipeline is consistent). In contrast, the variation in pore density of the right porous medium exerts a considerable influence on the leftward propagation of the explosion flame (the time for the flame to reach the left end of the pipeline varies significantly with the change of the right porous medium). In the working condition of porous medium with pore density of 30 ppi on the left and 10 ppi on the right, the flame propagating leftward still extinguishes after traveling a certain distance past the porous medium. The combined arrangement of porous media on both the left and right sides can effectively reduce the explosion overpressure. The explosion propagation velocity is the slowest and the explosion overpressure is the minimum under the working condition with porous medium with pore density of 30 ppi on the left and 20 ppi on the right.