The effect of biomass densification on combustion characteristics and particulate matter (PM) emission was studied in this work by means of thermogravimetric, combustion kinetic, and PM analyses with respect to the size distribution and elementary composition. Cornstalk as a typical agricultural biomass residue and camphorwood as a woody biomass were used in the experiment for comparison. It can be concluded that the biomass densification increases the ignition, burnout, and composite combustion indexes, leading to a better performance of biomass combustion. The main reaction mechanism of cornstalk pellets can be well-expressed with the chemical reaction series model, whereas the diffusion mechanism and chemical reaction series models can be applied to the combustion of camphorwood pellets. The biomass densification has little effect on the composition of PM but significantly changes the yield of PM. The influence of biomass densification on PM emission is related to the biomass properties. The densification significantly reduces the PM emission for cornstalk but significantly increases the yield of particles of aerodynamic cutoff diameters less than 1μm (PM1) for camphorwood.