Intermittent addition of steam was employed to increase the gasification reactivity of palm kernel shell biochar with CO2. The reactivity and variations in pore structures were initially assessed during CO2 and H2O-assisted gasification of biochars in a tube furnace, followed by characterization using thermogravimetric and surface area analysis. A quadratic orthogonal rotation regression combination design was used to investigate the effects of intermittent H2O addition on the total reaction time (t(100%)) of CO2 gasification. The achieving results showed that the formation of micropores with sizes of 0.3 to 1.5 nm was favored by CO, gasification, while the reactivity of biochar was highly correlated with the surface area of micropores of 0.93 to 1.47 nm. A pore expansion effect was the primary phenomenon observed during H2O gasification, while the reactivity of biochar with H2O was closely related to the surface area of pores with specific sizes. CO2 and H2O react with the biochar on separate active sites, and micropores of 0.93-1.54 nm are produced in the early stage of H2O gasification, which enhances CO, gasification. The intermittent addition of H2O increases the reactivity of biochar with CO2, such that the t100% value during CO2/intermittent H2O gasification is 31.89 and 15.80% lower than the values associated with using only CO2 or a simple mixture of CO2 and H2O.