Biomass char, obtained from the residues of biomass pyrolysis, was employed as feedstock for the gasification using an air-steam agent. The gasification with the energy self-sufficiency was carried out in a cyclone furnace where combustor and gasifier were combined into one reactor. The effects of equivalence ratio (ER) and steam to char ratio ( S/ C) on gasification performance were investigated. The results showed that the increasing ER led to the increasing reactor temperature and increased dry gas yield, H 2 yield and carbon conversion efficiency. The introduction of steam promoted the gas quality, but excessive steam would lower reactor temperature and degrade gas quality. Under the optimum experimental conditions (ER = 0.36, S/ C = 0.45), the yield of the tar-free gas reached 3.72 N m 3/kg and the LHV of the fuel gas was 4163 kJ/N m 3.