Abstract: Co-firing of coal boilers with biomass constitutes one of the efficacious approaches for reducing carbon emissions. The biomass particles are large and irregularly non-spherical, exhibiting gas-solid two-phase kinetic characteristics conspicuously different from those of spherical particles, which will exert an influence on their combustion process. The majority of the extant numerical simulation studies regarding coal boilers and biomass co-firing are deficient in discussions in this respect. Therefore, a non-spherical drag model is adopted to account for the influence of the irregular non-spherical characteristics of large biomass particles via the shape factor. A numerical simulation study is conducted on the co-firing of a 660MW hedging boiler and straw biomass, and the disparities with the spherical drag model are compared. The results indicate that: ①Compared with the spherical drag model, the non-spherical drag model is more accurate and rational in calculating the carbon content of fly ash, the trajectory of biomass particles, and the combustion process. The relative error of the carbon content of fly ash is merely 4.24%, and the calculation results of the non-spherical drag model under diverse loads are more in line with the experimental values. ②In contrast to the spherical drag model, the non-spherical drag model elevates the drag coefficient of biomass particles, and the velocity of the particles in the heating stage diminishes. At the same displacement, it achieves more thorough mixing with air and attains a higher temperature, with the ignition area being advanced. The biomass char undergoes more complete and rapid combustion, enhancing the simulation accuracy of the biomass burnout rate and the carbon content of fly ash. ③The burnout time of biomass particles escalates with the increase in particle size. When the equivalent particle size of the particles exceeds 3 mm, even if the shape factor is corrected, the accuracy will be significantly reduced, and it fails to accurately simulate the actual situation of real co-fired biomass.