Abstract: Biomass boilers were widely used as an effective method for biomass combustion. However, there were not many studies on the characteristics of atmospheric pollutants emitted from biomass boilers. Two biomass boilers with different structure were selected to study the emission characteristics of dust, PM₁₀ and PM_2.5 and compare it with coal-fired boiler. Wooden block fuel (MZ) and straw block fuel (JG) were used in this study. The results showed that the emission concentrations of pollutants from both biomass boilers could not fulfill Beijing local standard “Emission standard of air pollutants for boilers” (DB 11/139-2007). The emission factors using two types of biomass boilers showed a significant difference. For the wooden block fuel, the dust emission factors were 207.10mg/kg (BB1) and 465.51mg/kg (BB2); the PM₁₀ emission factors were 75.18mg/kg (BB1) and 149.61mg/kg (BB2); the PM_2.5 emission factors were 58.48mg/kg (BB1) and 106.86mg/kg (BB2) respectively. For the straw block fuel, the dust emission factors were 142.86mg/kg (BB1) and 1200.86mg/kg (BB2), the PM₁₀ emission factors were 63.63mg/kg(BB1) and 102.01mg/kg(BB2); the PM_2.5 emission factors were 50.90mg/kg(BB1) and 76.51mg/kg(BB2) respectively. Compared with the coal-fired boiler under the similar condition of thermal power, the average PM₁₀ emission factor of two biomass boilers was 30.41% lower than that for the coal-fired boiler, while the average PM_2.5 emission factor of two biomass boilers was 36.84% higher than that for the coal-fired boiler. PM_2.5 in the dust of biomass boiler has a higher proportion than that for the coal-fired boiler. Although biomass boiler has a very good applicable perspective due to its recycling applicability, the emission of atmospheric pollutants from some biomass boilers could not meet the local standard. Consequently, the current energy efficiency and dust removal efficiency should be improved to reduce the pollution to atmospheric environment.