Abstract: The modification of biomass fuel gas was studied in a fixed reactor with a certain amount of molten salts. The effects of temperature, static liquid height and superficial gas velocity on the outlet gas composition, the NaOH consumption, and the saturable absorption time of molten salts were investigated. The results show that the NaOH consumption increases from 59% to 83% and the biogas handling volume per unit molten salts is enhanced from 0.42 m³/kg to 0.48 m³/kg by elevating the temperature from 400 to 600 ℃. The CO conversion and the H₂/CO volume ratio of outlet gas both increase with the increasing of temperature and static liquid height, and decrease with the increasing of superficial gas velocity.