Abstract: In order to address such a problem of high yield tar with blockage and corrosion of facilities, iron-based catalyst were introduced in gasification process. In the meantime, the action mechanism of iron-based catalyst was analyzed based on the change of syngas composition in biomass gasification and the role of tar cracking. The results indicated that the yield of hydrogen in syngas elevated from 20.32 mL/g(biomass) to 114.72 mL/g(biomass) after adding iron-based catalyst. The macromolecular polycyclic aromatic hydrocarbons in tar were degraded. Iron as a catalyst propel the degradation reaction of cellulose chain end, which dissolve cellulose into furfural, ketone, furan and other compounds. This study provided a theoretical basis for the application of iron-based catalyst in gasification by confirming the catalytic effect of iron-based catalyst and revealing its catalytic mechanism.