Abstract: To thoroughly investigate the effects of thermal-oxygen coupling on the microstructure and spontaneous combustion properties of residual coal under high-temperature conditions in mines, this study focuses on gas coal from the Xinji No. 2 Mine in Anhui Province. By comprehensively employing multi-scale characterization techniques and molecular dynamics simulations, the study examines the evolution of the microstructure and spontaneous combustion properties of residual coal following 15 days of thermal-oxygen coupling pretreatment at 45 ℃. Using advanced experimental techniques such as low-temperature liquid nitrogen adsorption (BET), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), thermogravimetric analysis (TG), and cone Calorimetry, combined with Materials Studio molecular dynamics simulations, we systematically analyzed the independent contributions and synergistic effects of heat and oxygen during the long-term oxidation process of residual coal. BET analysis demonstrated that the thermal-oxygen coupling pretreatment increased the total pore volume of coal samples by 27.78%, significantly higher than the 2.70% observed in pure thermal pretreatment, confirming oxygen as the dominant factor in pore structure expansion. Molecular dynamics simulations further revealed that the oxygen diffusion coefficient of coal samples under thermal-oxygen coupling pretreatment increased by 773.59% compared to raw coal, markedly exceeding that of pure thermal pretreated samples, thereby validating the critical role of oxygen in enhancing pore mass transfer capacity at the molecular level. XPS analysis showed that the surface O/C atomic ratio increased from 0.93 in raw coal to 1.88 in thermal-oxygen coupled pretreated coal samples, while the relative content of carboxyl carbon (O—C=O) functional groups rose from 2.75% to 8.95%, indicating that thermal-oxygen coupling pretreatment significantly promoted surface oxidation of coal samples. EPR tests revealed that the thermal-oxygen coupled pretreated coal samples exhibited higher g-factor and free radical concentrations (N_g) during oxidation heating compared to raw coal and pure thermal pretreated samples, indicating significantly intensified free radical accumulation. TG analysis demonstrated a consistent downward trend in characteristic temperatures (T₁−T₆) for thermal-oxygen coupled pretreated samples relative to raw coal, with the dry cracking temperature (T₂) dropping by 33.10 ℃. Cone calorimetry tests showed the ignition time reduced from 84 seconds in raw coal to 48 seconds in thermal-oxygen coupled pretreated samples, while the peak heat release rate increased by 73.45% and the total heat release volume surged by 54.35%. These results indicate markedly enhanced combustion intensity and fire hazards. Based on the multi-scale representation and simulation results, a four-level synergistic evolution path of “porosity expansion-surface oxidation-radical proliferation-oxidation intensification” was constructed. The intrinsic logic of thermal-oxygen coupling-driven coal spontaneous combustion was revealed from four aspects: pore structure evolution, surface chemical activation, radical chain acceleration, and thermal effect. This provides a theoretical basis for the risk prevention and control of coal spontaneous combustion in high-temperature mines.