Biomass gasification for reburning is one kind of the most promising ways of biomass utilization.Different composition of syngas and tar will influence the NO reduction effect in the process of biomass gasification for reburning.A 10 kW updraft biomass gasifier was designed and built, and experiments on wood gasification were carried out to study the effect of oxygen content on the composition of syngas and tar.The relative content of the main gas species in the syngas rises with the air flow rate increase, but the relative content of phenolic compounds, which share a large part in the tar, declines with the air flow rate increase according to the experimental results.The study provides a theoretical guidance for the development of technology of biomass gasification for reburning.