This paper discusses the different methods for determining the kinetic parameters (activation energy and pre-exponential factor) of biomass (beechwood and flax shives) pyrolysis based on Kissinger method, isoconversional methods (Kissinger–Akahira–Sunose and Friedman) and based model (nonlinear least square minimization and optimization by genetic algorithm). Because of the widely dispersed values of activation energy and pre-exponential factor of three pseudo-components of the biomass (cellulose, hemicellulose and lignin) found in the literature, the pyrolysis of cellulose, hemicellulose and lignin was also studied. This paper shows that kinetic parameters are very sensitive to methods used. The comparison of results shows a large difference for the same experimental results even for pure pseudo-components. Based on results comparison, we think that Kissinger method remains the best method for kinetic parameters determination. Indeed, Kissinger relation takes into account the biomass structure effect and the mineral content. Isoconversional methods are also very suitable for low and medium conversion rate. Despite the fact that based methods are considered to be robust methods for the estimation of kinetic parameters in chemical engineering, these methods may misestimate the activation energy and pre-exponential factor for cellulose, hemicellulose and lignin.