The aim of this work was to model the thermal degradation of wood in an inert atmosphere at the cone calorimeter scale. First, the degradation of spruce wood was studied at the matter scale by TGA and DSC in an inert atmosphere at different heating rates. The kinetic parameters associated with a global multi-reaction mechanism were estimated by fitting the mass loss and the mass loss rate obtained by the TGA. The heats of reaction associated with the reaction scheme were estimated by fitting the heat flux measured by DSC. Then, experiments with an inert material (calcium silicate) were performed at the cone calorimeter scale under an inert atmosphere to characterize the boundary conditions of the developed 3D heat transfer model. The boundary conditions were determined by minimizing the difference between the measured in-depth temperatures and the predictions of the model using a least squares method. The results showed good predictions in agreement with experimental data and the convective heat transfer coefficients obtained were realistic. Finally, a 3D pyrolysis model, taking into account the anisotropic nature of wood, was developed by coupling the heat transfer with the kinetic model. The latter model was validated by comparison with tests carried out on spruce wood in an inert atmosphere using a cone heater.