Wood pyrolysis concerns the physical and chemical organic component decomposition under the action of heat in an inert atmosphere. To explain the phenomena involved in this process, the reaction mechanisms that take place during the thermal degradation of wood and its major components of cellulose, hemicellulose and lignin have to be identified. The number and the diversity of the results in the specialized literature illustrate the difficulty in explaining the complex kinetics involved during pyrolysis. This work proposes an innovative contribution to the modelling of wood treated at high temperature by proposing a theoretical approach at the micro-particle scale that allows a macroscopic modelling of the “thermal, chemical and physical” coupled phenomena to be realised. We will show how the cellulose, hemicellulose and lignin degradation models have evolved from a simplistic formulation towards complex reaction pathways which are at the origin of our model.