Abstract: In order to explore the influence of ionic liquids on the types and content of coal functional group, using infrared spectroscopy （ＦＴＩＲ） analysis technology, we studied types and content change of raw coal and the functional groups of coal after the treatment of ionic liquid and 1-ethyl-3-methyl imidazole acetate EMIm （Ａｃ）, 1-butyl 3-methyl imidazole acetate BMIm （Ａｃ） and 1-butyl 3-three fluorinated methyl sulfonic acid ester methyl imidazole salt （BMIm OTf）. The results showed that the coal contained fatty hydrocarbon, aromatic hydrocarbon groups and oxygen-containing functional groups, and the types of functional groups in coal remain the same after ionic liquid treatment. The content of most fatty hydrocarbons, aromatic groups and oxygen-containing functional groups in coal treated by ionic liquids decreased, which indicates that ionic liquids have certain destructive effects on coal functional groups. Among them, BMImOTf ionic liquid reduces the content of functional groups such as hydroxyl, carboxyl, fatty hydrocarbon branched chain, aromatic hydrocarbon and substituted benzene in coal. It has the best effect on the dissolution and destruction of the functional groups in coal, which is obviously superior to EMImAc and BMImAc.