Owing to the serious natural ageing phenomenon of ancient wooden buildings, to better explore the effect of drying and wet ageing degree on the exothermic behaviour of wood combustion, firstly, wood treated with different degrees of dry and wet ageings was obtained by artificially accelerating the dry and wet ageing method. The pore characteristics, along with the capacity of the heat transport of wood treated and wood combustion heat flow with different dry and wet ageing degrees, were analysed by scanning electron microscopy, thermophysical property, and thermal analysis test. Finally, according to Friedman’s differential equivalent conversion method, the reaction process of the distribution of apparent activation energy of wood in various exothermic stages was computed and appraised, revealing the mechanism of the effect of the wood treated with dry and wet ageings on thermal reaction process. In the accelerated exothermic stage, the initial dry and wet ageing process (10 to 30 times) led to the opposite change in the trend of the apparent activation energy of wood and the fresh wood as a whole. The effect of the dry and wet ageings on the energy demand of the oxidation reaction at the end of prompt exothermic stage could decrease with the deepening of the ageing degree.