This study addresses the issue of spontaneous combustion in the goaf of the 11223 working face in Xiaojihan Mine. A 3-D model of the goaf was constructed using numerical simulation methods, incorporating actual working face parameters and the porous media fluid dynamics equations. The spatial distribution patterns of oxygen mass fraction, air-flow velocity, and turbulent kinetic energy in the goaf were simulated. The oxygen concentration distribution and air-flow characteristics in the goaf were analyzed, and the "three zones" of spontaneous combustion were delineated. The results indicate that the oxidation zone on the intake side ranges from 70-105 m (width of 35 m), the middle part of the goaf ranges from 40-75 m (width of 35 m), and the return side ranges from 10-25 m (width of 15 m), consistent with field measurements. The study reveals the non-uniform characteristics of the oxidation zone in the goaf, providing a theoretical basis for coal mine fire prevention and control.