Abstract: Under the background of green and low-carbon development of energy, the clean and efficient utilization technology of biomass energy has become a hot spot of current research, which provides technical support for the gradual replacement of coal resources by biomass energy. The physical conditions that affect the combustion efficiency mainly include the particle size of the fuel particles, different combustion conditions, and the surface characteristics of the fuel particles. For this reason, the microstructure of cow dung particles with different particle sizes and their combustion products under different working conditions was visually observed by transmission electron microscopy. The specific surface area detection method was used to compare the characteristics of pore size and specific surface area of each particle of raw cow dung with different particle sizes and ash samples obtained under different working conditions, and the combustion effect of each group of cow dung was obtained by elemental analysis. Through the extraction and calculation of the characteristic parameters of each particle, the combustion effect of each sample is discussed. The results show that if the particle size of cow dung is too small and the air volume is too large, it is not suitable for combustion. The factors such as air volume, combustion temperature and particle size have an impact on the combustion process of cow dung, and the effect is not monotonous; among the three particle sizes, 200 μm is more suitable for combustion, and as the particle size of cow dung is closer to a reasonable value, the influence of working conditions on combustion effect is narrowing. Through the comparison of 6 groups of test results, the combustion effect is the best when the particle size of cow dung is 200 μm and the feed rate is 115 kg/h and the air volume is 101 m³/h. For the adsorption of ash particles, the adsorption effect is better when the ash particle size is larger under low pressure adsorption. Under high pressure conditions, the adsorption effect of ash particles with smaller particle size is better. Through the HRTEM method, the lattice fringe size of the ash sample is larger than that of the cow dung particles.