In this study, the catalytic effect of biomass leachate from corn straw (CS) and corncob (CC) on CO2 gasification of high-rank coal was investigated. The coal char was pretreated by impregnation with biomass leachate. The isothermal gasification of char was performed using a thermogravimetric analyzer (TGA) at temperatures of 1100, 1200, and 1300 degrees C. The model-free, model-fitting, and nucleation model were adopted for the kinetic analysis. The carbon structure, the surface morphology, and element composition were further evaluated. The results showed that the CS and CC leachate can effectively accelerate coal char gasification at high temperatures, reducing the activation energy by 53.4 and 66.1 kJ/mol, respectively. The model-fitting analysis showed that the volume model (VM) or random pore model (RPM) had a better fitting performance than the grain model (GM). The structure analysis indicated that the active sites and porosity of the pretreated coal char increased during gasification, which was due to the attachment of the inorganic and organic species from biomass leachate. In addition, the predictions for isothermal gasification over a temperature range of 1100-1300 degrees C were made with respect to the specific reaction time.