Based on the ASPEN PLUS platform, the biomass pyrolysis gasification model was established by using the gas-solid reaction kinetics in the flue gas atmosphere generated by the biomass pyrolysis gas combustion. The kinetics of pyrolysis biomass was analyzed by AKTS in simulative flue gas (80%N2, 17%CO2 and 3%O2). The simulation results were compared with the experimental values to verify the validity of the model, and the number of reactors was determined by analyzing the atmosphere influencing the pyrolysis gasification characteristics. The results showed that the simulation performance of biomass gasification based on ASPEN PLUS platform was favorable. The model was closer to the actual countercurrent flow reaction with the increase of the number of kettle. In order to ensure the accuracy of simulation, it was more appropriate to choose the number of reactors in series 4. During the process of biomass pyrolysis gasification, the activation energy (E) and the pre-exponential factor (A) of the kinetic parameters were not fixed values but changed with the increase of the reaction temperature. The pyrolysis gasification reaction did not follow a single reaction mechanism, which was composed of multiple steps. Compared with the nitrogen and oxygen atmosphere, the flue gas atmosphere was favorable for the production of CO. The calorific value of gas was increased by 1.3 times, which was mainly caused by the increase of volume of CO and CH4.