Abstract: Biochar powder is one of the principle byproducts from the biomass pyrolysis process and its removal efficiency from the pyrolysis vapor affects the quality of subsequent oil product significantly. In this study, the dust removal characteristic of a cyclone was investigated experimentally on a drop-tube fast pyrolysis reactor. In this reactor, dust concentration in the pyrolysis vapor before entering the cyclone of was about 35-50 g/m3 and varied randomly. Results showed that 91% of particles of char dust collected in the cyclone were between 0.39 and 30 μm in size. And amount of particles which were smaller than 0.39 μm or bigger than 40 μm were negligible. The dust removal efficiency of the cyclone was less than 80%. With the increase of the dust concentration in pyrolysis vapor, the dust removal efficiency of the cyclone increases slightly.