Abstract: With the increasing depth of coal seam mining, the initial load-bearing stress and ambient temperature of the coal body are gradually increased, leading to increasingly prominent coal fire disaster risks in deep shaft mining. To investigate the damage caused by different initial load-unloading crushing processes and pressure-unloading-pre-oxidation processes on the microstructure of crushed coal, as well as the influences imposed by these processes on oxidative heat release characteristics, the microstructural and oxidative spontaneous combustion characteristics of unloaded crushed coal were systematically studied by means of experiments such as low-temperature nitrogen gas adsorption, simultaneous thermal analysis, and in-situ diffuse reflectance infrared spectroscopy. The results indicate that in the load-bearing-unloading crushing process, the fractal dimension of the unloaded crushed coal is increased with the increase of initial load stress; the expansion of the coal body skeleton and the breakage of chemical bonds are triggered by load-bearing-unloading, and the content of reactive functional groups is increased, by which the starting temperature of coal-oxygen composite is reduced, the reaction rate is accelerated, and the low-temperature oxidative heat generation tendency of the coal is strengthened. In the load-bearing-unloading-pre-oxidation process, the fractal dimension of the unloaded crushed coal is increased with the increase of pre-oxidation degree, and the initial high-temperature oxidation and oxidative heat production tendencies of the coal body are enhanced; in the pressure-unloading-pre-oxidation process, the fractal dimension of the unloaded crushed coal after pre-oxidation treatment is increased, and a secondary adhesion effect of coal particles is exhibited during the initial high-temperature oxidation process. It is found that the development of micropores and mesopores can be promoted by initial low stress and initial oxidation at 120 ℃, whereas the pore structure is destroyed by excessively high pre-oxidation temperatures. Specifically, lower low-temperature oxidation starting temperatures, lower reaction heat requirements, and faster reaction rates are exhibited by coal samples in the 120 ℃ initial high-stress group and the 180 ℃ initial low-stress group, indicating a stronger oxidation tendency. With the increase of pre-oxidation temperature, the contents of —COOH, —CHO, and —OH in the unloaded crushed coal are increased, while the content of methyl cluster structures is initially increased and then decreased; the accumulation of reactive methyl clusters inside the unloaded crushed coal is dominated by pre-oxidation at 120 ℃, while the depletion of —CH₂ and —OH, as well as the formation of —CH₃ and —CHO inside the unloaded crushed coal, are dominated by pre-oxidation at 180 ℃. A positive correlation is exhibited between the level of functional groups in the pre-oxidized unloaded crushed coal with low initial stress and the bearing stress, and the range of 8−16 MPa is identified as the critical initial stress interval for changes in microstructure and oxidation characteristics. Microstructural damage is caused to the unloaded crushed coal by elevated initial stress, by which its spontaneous combustion tendency is enhanced; a synergistic effect is exerted by the initial static stress-unloading process and the pre-oxidation process on the changes in coal oxidation characteristics, while the spontaneous combustion risk of the leftover crushed coal is reduced by the synergistic effect of excessively high initial stress and pre-oxidation temperature. A composite mechanism of the combined effect of bearing stress unloading and high-temperature pre-oxidation on the leftover coal in the mining area is revealed, and theoretical references can be provided by the results of this study for the safe mining of deep coal seams and the engineering practice of re-mining and recycling of the leftover coal in goafs.