Abstract: Biomass gasification is one of the most important approaches to produce low-carbon fuel gas. It is often required to lighten the tar components under the directed and efficient generation of fuel gas components, such as H₂, CO, and CH₄, during production. This study aims to systematically review the reaction patterns of biomass pyrolysis, volatile reforming, and char gasification under the different gasifying agents, including H₂O, CO₂, and H₂. An investigation was also made to explore the influence mechanisms of the reaction conditions (temperature, pressure, catalysts, and reactors) on the biomass gasification with different gasifying agents. Some strategies were proposed to regulate the generation of the fuel gas products. An analysis was then performed on the fuel gas production capacity, gasification efficiency, and carbon emission in biomass gasification. Finally, the pressing challenges and countermeasures were proposed for biomass gasification for fuel gas production. The results reveal that the high reaction temperature promoted the biomass conversion, tar cracking, and the generation of H₂ and CO. However, excessively high temperatures caused the catalyst particles to grow and deactivate. The equilibrium of the methanation reaction was then limited to inhibit CH₄ production. From a kinetic perspective, the reaction pressure increased the concentration of the gasifying agent and then prolonged the residence time of volatiles, leading to the high reaction rates of biomass and its pyrolysis volatiles. From a thermodynamic perspective, the high pressure facilitated the methanation reactions of the biomass volatiles and char. The CH₄ generation was promoted unfavorable for the reactions, such as volatile reforming, carbon dioxide gasification of char, and steam gasification, thereby reducing the yields of CO and H₂. Alternatively, the catalysts promoted the tar cracking for the high production of fuel gas. Previous catalysts were typically in a state of particle separation from biomass, making it difficult to enhance biomass conversion rates. An effective approach was represented to load the catalysts directly onto the biomass, and then catalyze the pyrolysis and gasification of its native chemical structure. Thereby, the high biomass conversion rates and fuel gas yields were achieved within the short particle residence time. Among them, the fluidized bed was the better choice for the biomass catalytic gasification. Rapid transfer rates were offered at the moderate reaction temperatures. The supported catalysts served as the fluidization carriers for the excellent contact with the biomass. There was a more efficient catalytic conversion of biomass into high-heating-value fuel gas under the gasifying agent of H₂O, CO₂, and H₂. Specifically, the 1.01 m³ of H₂, 0.67 m³ of CO, and 0.44 m³ of CH₄ were directionally produced per kilogram of biomass gasified, respectively. Moreover, the biomass gasification for the fuel gas production exhibited a carbon sink. Therefore, the "green methane" was produced by biomass steam gasification coupled with hydrogenation gasification and CO₂ methanation. Currently, the primary challenges of biomass gasification are to efficiently lighten the tar components and the catalyst deactivation due to carbon deposition, in order to maximize the biomass gasification within the short particle residence times. An integrated experimental-simulation approach was employed to explore the optimal kinetic-thermodynamic coupling parameters for biomass gasification. The low-cost and highly active composite catalysts were developed for the direct catalytic conversion of biomass. For instance, the Fe-catalyzed direct hydrogenation gasification of biomass was achieved in a 91.4% biomass conversion rate and a 43.0% CH₄ yield, along with the co-production of the light liquid aromatics, within a particle residence time as short as 30 min. It is of significant importance for the future of biomass gasification. This finding can advance the fundamental scientific understanding of the complex chemical reaction networks in biomass gasification for fuel gas production. The robust theoretical guidance and data references can help optimize, control, and practically implement biomass gasification.