This work is related to the modeling of cellulose pyrolysis with a pseudo equilibrium approach. The objective is to model the kinetics of the cellulose pyrolysis with a semi-global mechanism obtained from the literature, in order to obtain the yield and the rate of formation of char. The pseudo equilibrium approach consists on the assumption that the solid phase devolatilization can be described kinetically, preserving the competitive characteristics between the production of char and tar, while the gas phase can be considered in chemical equilibrium. A set of ordinary, linear and nonlinear, differential equations was obtained and solved numerically with a simple but consistent scheme using the Totally Implicit Euler method. Chemical equilibrium was solved using CANTERA coupled with a code written in Matlab. Results showed that the scheme preserves the tar-gas competitive characteristic for cellulose pyrolysis. The gas phase, defined as a mixture of CO2, CO, H2O, CH4, H2 and N2, showed similar composition compared to models from literature. Finally, the extension of the model to biomass in general is straightforward, in order to include the hemicellulose and lignin.