Abstract: In order to explore the emission characteristics of particulate matter during the co-combustion of biomass and municipal sludge, combustion tests were carried out using a vertical fixed-bed system coupled with a Dekati Low-pressure Impactor in this work. The particle size distribution and elemental composition characteristics of the particulate matter in flue gas were obtained, and the influence of the interaction effect between different biomasses and municipal sludge on the emission of particulate matter was revealed. The results showed that the emission yield of particulate matter during the combustion of straw biomass was the highest, which was much higher than that generated during the individual combustion of municipal sludge. In contrast, the emission yields of particulate matter from woody biomass and shell biomass were relatively lower. Particulate matter generated during the combustion of all three types of biomasses was mainly submicron particulate matter (PM₁), accounting for 93.3%–96.6% of the total PM₁₀ emission. Among them, the main chemical compositions of PM₁ were alkali metal chlorides and sulfates, while the ultra-micron particulate matter (PM_1–10) mainly consisted of alkaline earth metal silicates and aluminosilicates. The addition of municipal sludge could significantly reduce the PM₁ emission. The physical dilution effect and the interaction reaction between components jointly promoted the transformation of PM₁ into coarse particles and bottom ash, thus reducing the total PM₁₀ with the maximum reduction rate of 62%. The inhibitory effects of the component interactions between different types of biomasses and municipal sludge on particulate matter generation are as follows: straw biomass > woody biomass > shell biomass.