Abstract: In order to explore the effect of different oxygen concentrations in mine goaf on the microscopic characteristics of coal during low temperature oxidation process, we simulated coal oxidation at low temperature under different oxygen concentrations. Through BEL-Max automatic specific surface/pore analysis, steam adsorption instrument and electron spin resonance spectrometer (ESR), the change characteristics of pore distribution and free radicals during low temperature oxidation of coal under different oxygen concentrations were obtained. The experimental results show that with the increase of oxygen concentration and oxidation temperature, moisture, volatile matter, BET specific surface area and free radical concentration change in stages. After 130 ℃, the recombination rate of coal and oxygen is accelerated, and the continuous decrease of moisture and volatile matter leads to the development of coal pores, increases the active surface contact area between oxygen and coal, activates the original inactive primary free radicals, participates in the reaction and produces more new free radicals. In the heating range of 200 ℃, the concentration of free radicals (21%) increased by 12.77 × 1017/g.