Abstract: Spontaneous combustion of coal is the main cause of fire in coal mine.The macroscopic performance is the continuous accumulation of the coal spontaneous combustion release heat，and finally leads to a fire caused by the temperature rise of the coal body.The microstructure shows that the active functional group in the coal is continuously reacted with oxygen to generate heat，and the types and quantity of the micro-structures of different kinds of coal can lead to different spontaneous combustion tendency of the coal.In order to study the original spectrum of typical Yanghuopan long flame coal，the variation of infrared structure parameters of characteristic temperature points and the migration law of main functional groups，the change of functional groups in the process of coal oxidation was measured by in situ diffusion reflection Fourier transform infrared spectroscopy system，and the wave spectrum of the original coal of long flame coal was obtained.The original spectrum was fitted by Origin，and the content of each functional group was obtained.The infrared structure parameters at different characteristic temperature points were calculated and analyzed，and the comparison analysis was carried out with Yangquan anthracite.The results showed that the internal surface area of long flame coal in the original coal was large，the internal structure was loose，the hydrogen content of fat was more，the length of fat chain was short，the degree of aromatic condensation was low，and spontaneous com-bustion was more likely to occur.With the increase of temperature，the structural parameter I1 of long flame coal was smaller than anthracite，the structure parameter I2 of long flame coal was larger than anthracite，and the structure parameter I3 of long flame coal decreased at first and then increased.The hydroxyl，aliphatic hydrocarbons and oxygen-containing functional groups in long flame coal were active groups，which were mainly affected by their own hydroxyl content，alkyl side chain and long chain of fatty hydrocarbons.They changed greatly in the process of coal oxidation and had great influence on the oxidation of coal.The change of aromatic hydrocarbons in long flame coal was small and relatively stable.