The purpose of this study is to develop a numerical tool to predict the mass loss of a wood board during heat treatment as a marker of the process advancement. Mass loss dynamics during the wood heat treatment is experimentally obtained using a specially conceived equipment. The investigation method is applied on large scale wood samples whose radial and transvers dimensions are close to the boards used in industry. A two-step reaction mechanism is adopted to describe the behavior of wood thermodegradation. Model parameters are obtained by fitting the experimental data according to a new approach developed in this study for their optimal determination. The originality of the implemented modelling strategy is the establishment of a three-stage approach based on the analysis of wood thermal sensitivity depending on the treatment temperature range. Model equations are solved numerically by the commercial package Matlab® software. A good agreement is achieved between the numerical predictions and the experimental data. The developed model and established kinetics can be used for heat treatment process and reactor design in industry to produce wood materials for their applications.