Biomass char gasification is an important part of biomass conversion technology; the addition of additives can effectively change the gasification reaction rate of char. The kinetic characteristics of steam gasification reaction of biomass char particles were explored by adding CaO, Fe2O3, and Ca-Fe mixed catalyst to biomass, and the apparent activation energy and pre-exponential factors of char particles were obtained. Experimental results show that the kinetic reaction process of char steam gasification follows the shrinking cylinder model. Through linear fitting, it can be obtained that there is a good linear correlation between activation energy and pre-exponential factor, which follows the dynamic compensation effect. Under the same temperature conditions, CaO can accelerate the reaction rate of char, while Fe2O3 can delay the gasification rate of char particles because of sintering phenomenon at high temperature. The synergistic effect of Ca-Fe can reduce the total activation energy of the reaction. The addition of CaO can greatly change the kinetic performance of the Fe2O3 catalyst, inhibit the sintering deactivation reaction of Fe2O3 at high temperature, increase the diffusion path of steam, and promote the char steam gasification reaction.