In order to find out the optimal concentration of ionic liquid to lower the cost of inhibiting coal spontaneous combustion, effects of aliphatic hydrocarbons, hydrogen bonds, and some structural parameters of coal samples treated with low‐concentration ionic liquids were analyzed through Fourier‐transform infrared spectroscopy (FTIR) and temperature‐programmed experiments. Meanwhile, the changes of index gases in the heating process were observed by the temperature‐programmed method. The results show that the contents of aliphatic hydrocarbons in the treated coal samples decrease remarkably, so does the length of aliphatic chain CH₂/CH₃; besides, the amount of CO produced also decreases to some extent. When the mass concentration ratio is 1:10, HB‐tc, BB‐tc, AC‐tc, and BN‐tc can reduce the spatial structure and enhance the structural stability of aromatic clusters in coal. The CO concentrations of 1:2 HB‐tc and 1:10 AC‐tc are obviously lower than that of raw coal, indicating their better inhibitory effects. The inhibitory effect of HB‐tc decreases with the decrease in concentration. With the rise of temperature, the effect of concentration on the inhibition of CO production gradually weakens at 180°C and 200°C. AC‐tc achieves the optimum inhibitory effect near 1:10 mass concentration ratio.