In this work, the emission of particulate matter (PM) from combustion of agricultural biomass was investigated in comparison to woody biomass. The mechanism of PM emission was studied by means of mass-based particle size distributions (PSDs), inorganic elemental component analysis and morphology at variant combustion temperatures, and different biomass feedstocks. The mass-based PSDs of PM10 of cotton stalk, rice husk, and camphor wood exhibit a bimodal distribution, while that of corn stalk exhibits a unimodal distribution. The,emission of PM10 of agricultural biomass is much higher than that of woody biomass, and it is mainly composed of PM1, in which Na and K are enriched as alkali metal chloride and sulfide. On the other hand, Mg and Ca are enriched as the main inorganic, compounds in PM1-10 for woody biomass. A higher combustion temperature is favorable for the formation of fine PM particles against a reduction of PM10. PM1 and PM1-10 formation mechanisms are different for different biomass feedstocks, and their formation pathways are hereby proposed for each biomass resource.