According to computational fluid dynamics, heat transfer theory, and chemical reaction kinetics theory, the models of single-pellet biomass combustion were established, flow, heat transfer and mass transfer of single-particle biomass fuel during combustion were analog calculated, and they showed about 2 min, a 2 cm biomass pellet fuel completely burnt out , the highest temperature is 1280 k, the release of gases such as H2O, CO2 and CO. The bed combustion model of biomass chain furnace was built based on the single particle fuel combustion model means the bed combustion process of biomass particles is in good agreement with the actual combustion process. This study provides a theoretical basis for the whole biomass briquette boiler system design and performance optimization and improvement.