Catalytic coal gasification was studied by using thermal desorption spectroscopy （TDS） under high vacuum conditions. Activated charcoal was used as a model compound of coal, and Na₂CO₃ and K₂CO₃ as catalysts. Catalysts enhanced oxygen adsorption and decomposed at temperatures below their own decomposing temperatures. After pretreatment of the catalyst at high temperature the CO₂ desorption pattern represented characteristics of reaction intermediates. There were two peaks, -peak and -peak, in CO₂ TDS curves. From the experimental results, -peak was interpreted to the result from intercalatd metal-carbon (M-C) complex, and -peak from metal-oxygen (M-O-C) complex. A higher pretreatment temperature led to decrease both the number of M-O-C complex and its thermal stability. The increase of catalyst loading in Na₂CO₃-containing sample resulted in relative increase of the number of M-O-C complex than that of intercalated M-C complex, and also increase of thermal stabilities of both reaction intermediates. Major difference between K₂CO₃ and Na₂CO₃ appeared in -peak, intercalated M-C complex. That is, the contribution of intercalated metal-carbon complex to total reaction intermediates was larger in K₂CO₃ than Na₂CO₃. This could be attributed mainly to the better intercalating ability of potassium due to its lower ionization potential.