Abstract: The effects of ultrafine chemical inert SiO2 and active NaHCO3 powder on the premixed laminar flame of methane-air mixtures were studied experimentally. High speed camera and schlieren system were applied to investigate the flame microstructure and variation of flame propagation. Also,the history of explosion overpressure was probed. Re- sults indicate that the flame propagation is enhanced by the turbulence when a small amount of ultrafine SiO2 powder is added,with the concentration of ultrafine SiO2 powder in the order of 50 g / m3 ,the flame propagation velocity is en- hanced 100% ,and the effect of physical flame propagation mitigation is appeared gradually with the increase of con- centration of SiO2 powder. Flame propagation velocity is suppressed significantly with the addition of ultrafine NaHCO3 powder,and the flame front is divided into honeycomb,the degree of suppression is proportional to the NaHCO3 powder concentration,and the explothe order of 150 g / m3 . Compared to the addition of SiO2 powder,the explosion overpressure increase is slowed down significantly when NaHCO3 powder is added into the methane-air mixtures.sion flame is suppressed completely with the concentration of ultrafine NaHCO3 powder in