In the computational particle fluid dynamics method, a numerical model of a three-dimensional circulating fluidized bed (CFB) air-water vapor mixture was established. This model facilitated an investigation of the characteristics of the biomass gasification process in a CFB gasifier. This study systematically examined the impact of variables such as fluidized gas velocity, gasification temperature, air equivalent ratio, and water vapor ratio on the spatial distribution characteristics of the gasification products. The results indicated that the increase in the fluidized gas velocity was correlated with a gradual reduction in the combustible gas concentration at the gasifier outlet. The increase in gasification temperature led to a decrease in CH4 content at both the furnace and gasifier outlets. Meanwhile, the CO and H2 content increased at these locations. A more balanced component distribution was observed at a gasification temperature of 1073.15 K. Moreover, increasing the air equivalent ratio resulted in a decrease in the flammable gas content at the furnace and gasifier outlet, enhancing a more uniform component distribution at an air equivalent ratio of 0.26.