Abstract: The growth characteristic of biomass-fired PM_2.5 with vapor condensation was studied. A growth tube was employed to investigate the growth performance of PM_2.5 at various temperatures of water, initial concentrations of particles, residence times and surfactants. The results show that the growth performance of PM_2.5 from biomass combustion is better than that of coal-fired PM_2.5 with vapor condensation. Furthermore, both the water temperature increase and the residence time delay benefit the growth of PM_2.5. Unlike the growth of PM_2.5 from coal combustion, the growth of small size of particles is seldom affected by the initial particles concentration. However, with a certain amount of surfactant addition, the particles can all grow up to 1 μm .