Abstract The stable structure and the time-varying behavior of stoichiometric methaneair flames on a porous metal burner at atmospheric pressure were studied using a numerical model which includes detailed chemical reactions. It has been confirmed that the model gives quantitative agreement with experiment for stable flame structures such as flame temperature, radical concentrations, and standoff distance, and also flame oscillation. It was shown that the overall activation energy and the standoff distance increase increase rapidly in the region of flame temperature < 1550K. Furthermore, it was also confirmed that the flame intrinsically oscillates due to the propagating time lag of the temperature disturbance from the burner surface to the reaction zone, and its instability is enhanced by a large standoff distance. On the basis of these results, it is asserted that the critical flame temperature for the stability of stoichiometric methaneair flames on porous plug burner is near 1550K.