Abstract: In order to explore the influence of quenching effect of porous media and the explosion overpressure up- stream of porous media under the synergistic effect of ultra-fine water mist and porous media,an experimental platform of transparent plexiglass gas explosion pipeline with the size of 80 mm×80 mm×1 000 mm was designed to research the synergistic inhibition effects of ultrafine water mist concentration,pore density and porosity factor on the flame propaga- tion and explosion overpressure of 9. 5% methane / air premixed gas. The experimental results show that the maximum flame front propagation velocity and the maximum explosion overpressure have a significant diversification in the up-stream of porous material by changing the concentration of ultrafine water mist,pore density and porosity factor. With the increase of ultra-fine water mist concentration,the peak flame front velocity and explosion overpressure decrease gradually,and the time of explosion overpressure peak appears shorter. As the aperture decreases,the flame front prop- agation velocity decreases and the pressure attenuation rate increases significantly. At the same time,the combination of ultrafine water mist and porous material has a synergistic inhibition effect on the methane / air explosion. A large amount of heat energy can be absorbed by ultra-fine water mist into the pipeline,which reduces the reaction rate and flame propagation speed. In addition,the porous material absorbs some of the precursor shock waves and destroys the positive feedback mechanism. Therefore,the synergistic inhibition effect of the two materials is better than the single inhibition effect. The porous material placed in the pipeline makes the propagation flame quenched,and ultrafine water mist added reduces the overpressure upstream of the porous material. However,once the quenching of porous media fails,the flame turbulence would intensify,which may lead to more serious accidents. In addition,compared with the 9． 5% methane / air premixture,under 87% porosity factor,20 PPI pore density and 1 453. 1 g / m3 ultra-fine water mist concentration,the flame front propagation speed was 12. 8 m / s,the decrease rate reached 44. 23% and the maximum explosion overpressure in the upstream of the porous material was 6. 13 kPa,which was reduced by 40. 62% ,the inhi- bition effect was the most obvious.