Abstract: The side chain functional groups in coal are important factors affecting the hydrophilicity and hydrophobicity of coal. In order to reveal the interaction mechanism between side chain functional groups in coal molecules and water molecules, the non-covalent bond forces between the side chain functional groups of 24 coal molecules and water molecules were calculated based on the density functional theory.The results show that the side chain functional groups interact with water molecules mainly through hydrogen bond force, accompanied by van der Waals force, and almost no repulsive force. The weakest total hydrogen bond energy of oxygen-containing functional groups with water molecules is -10.91 kJ/mol, and the strongest is -71.03 kJ/mol, where a small part of the oxygenic functional group can bind to two or more water molecules.The total hydrogen bond energy of nitrogen-containing functional groups with water molecules ranges from -30.70 kJ/mol to -6.44 kJ/mol.The total hydrogen bond energy of sulfur-containing functional groups with water molecules is stable at about -12.00 kJ/mol.The hydrophilic ability of the side chain functional groups from strong to weak is as follows: carboxyl, hydroxyl, carbon, aldehyde, ether bond, amino and polar bonds.The research results provide a new way for surfactants or dust suppression agents to enhance the hydrophilicity of functional groups, thereby improving the hydrophilicity of coal and enhancing the dust removal effect.