With the aim to ensure biomass entrained-flow gasification in a slagging gasifier, the characteristics of biomass fusing ash using CaO and Fe2O3 as fusing agent were investigated respectively by experiments. Subsequently, the influence of fusing agent on the gasification reactivity of biomass chars was studied. The results indicate that when the weight percent of CaO is 0.3～0.4, the melting point drops down apparently; when the weight percent of CaO is higher than 0.4, the melting point increases. While the addition of Fe2O3 increases at 0～0.5, the melting point decreases sharply. When the amounts of CaO and Fe2O3 are low, they can promote the reaction rate of char gasification. However, as the amounts of two additives increase, the fusing agents attach on the porous surface of chars and prevent the gas from the surface of chars, so the gasification reactivity decreases.