<p>In terms of long-term survival, ancient building wood has undergone dry and wet ageing, due to the influence of water adsorption and desorption in an atmospheric environment. To study the impact of the dry–wet ageing process on the pyrolysis kinetic behaviour of wood, this study designed an artificial accelerated dry–wet ageing simulation experiment to obtain dry–wet ageing wood similar to ancient building wood. Furthermore, pyrolysis tests were conducted during the study of the pyrolysis characteristics of wood with different degrees of dry–wet ageing. Through the peak characterisation method, the evolution of the thermal mass loss characteristic peaks in the water evaporation and pyrolysis stages as dry–wet ageing was discussed. Three isoconversional methods were used to analyse the variation characteristics of thermodynamic parameters with the increase of dry–wet ageing extent. The reaction mechanism function of pine pyrolysis behaviour with different dry–wet ageing degrees was determined, and the evolution mechanism of pyrolysis reaction mechanism with the deepening of dry–wet ageing degree was revealed. The consequences suggest that the peak mass loss rate of wood at different dry and wet ageing extents increases linearly with the increase in heating rate. The alteration of the average apparent activation energy (<i>E</i>_<i>α</i>) of wood affected by the degree of dry–wet ageing basically conformed to the sinusoidal damping model. The change in dry–wet ageing degree would cause the energy demand threshold of wood’s internal reaction to change greatly. The finding supplements the theoretical foundation of fire hazard evaluation of ancient buildings.</p>