Porous media combustion technology has a wide range of application prospects due to its good combustion stability. Combined with the Venturi mixer, which is widely used in the industrial premixing field, the non-uniformity of the premixed CH4/air gas from the Venturi mixer is evaluated by the spatial mixing deficiency (SMD). At the inlet velocity of 0.8m/s and the excess air coefficient of 1.4, the influence of SMD on the combustion stability of porous media was studied. The results indicated that SMD, which is less than 2.5%, has little effect on the stability of the porous medium combustion flame. With the increase of SMD, the area of the high-temperature combustion zone further increases, and the maximum combustion temperature increases linearly; The stable range of combustion decreases with the increase of SMD.