Abstract: Biomass gasification in the presence of steam was carried out to produce bio-gas in a fluidized bed reactor. The installation was made up of a fluidized bed reactor and a fixed bed cracking reactor. The feedstock was sawdust and the cracking catalyst included calcined dolomite and nickel-based reforming catalyst. The results showed that H2/CO (H/C) mole ratio greatly increased with increasing gasification temperature and steam/biomass mass ratio，but did not change much with increasing catalytic cracking temperature. In addition，in the catalytic cracking reactor using different kinds of catalysts would lead to different H/C. Two sections of catalytic cracking were used，sectionⅠwith calcined dolomite，and section Ⅱwith nickel-based catalyst. The tar cracking rate reached 96.70%. Using two sections of catalytic cracking not only would increase the tar cracking rate，increase the yield of H2 and CO，purify the biogas，but also could prevent the nickel-based reforming catalyst deactivation and extend its service life.