Abstract: The influence of alkali metal volatilization on the performance of nickel-based catalyst in the steam gasification of cellulose biomass was investigated in a two-stage fixed bed reactor. The results show that potassium is deposited on the catalyst surface with the volatilization of potassium salt during the catalytic steam reforming of potassium-loaded cellulose. The existence and deposition of proper amount of potassium may suppress the coke deposition and enhance the activity of nickel-based catalyst, which is of benefit to producing more hydrogen in the steam gasification of biomass. However, excessive amount of potassium loaded in cellulose may reduce the activity of nickel-based catalyst; moreover, with the repetitious operations, potassium is accumulated on the catalyst surface, which may lead to an obvious inhibitory effect on the activity and stability of nickel-based catalyst in the steam gasification of biomass.