Advanced and low-cost catalytic materials (catalysts) play an enabling role in tar cracking for biomass gasification technology and contributing to reducing CO₂ emissions. Herein, a biochar supported Fe-Mo carbides catalyst was synthesized by impregnation method combined with in-situ carbothermal reduction from abundant biomass raw materials. The catalytic performance over a series of Fe-Mo carbides catalysts was examined by a two-stage pyrolysis-catalysis reactor. The addition of Mo species promoted the carbon solvation on the surface of Fe particles to form Fe₃C active sites which further etching the carbon support with an abundant mesoporous structure. Fe-Mo_0.5@C catalyst demonstrated a high tar cracking efficiency of 91.05% and remained at 84.77% after 5 cycles. The tar conversion pathways were summarized based on gas yields and components of residual tar. The Fe₃C-Mo₂C active sites contributed to the cleavage of oxygen-containing macromolecules to generate light aromatic hydrocarbons and phenolic substances with stable structures. Besides, the carbothermal reduction regeneration was carried out under N₂ atmosphere at 800 °C to obtain regenerated catalysts to overcome coke deposition and metal oxidation, which recovered the tar conversion efficiency to 90.41%. The tar catalytic cracking mechanism over biochar supported Fe-Mo carbides catalyst was also first proposed. The results showed that biochar supported Fe-Mo carbides catalyst is a promising catalyst for efficient biomass tar catalytic cracking.