Abstract: The present invention discloses a method for constructing and optimizing a molecular structure model of lignite, comprising: collecting and processing a lignite sample, analyzing a lignite experimental sample, calculating the number of carbon atoms in lignite and the number of carbon atoms in other parameters, obtaining the sizes of aromatic clusters, and determining the composition features and number of aromatic structural units in lignite; calculating the total number of carbon atoms and the number of aliphatic carbon atoms in lignite; obtaining the categories and number of oxygen-containing functional groups in lignite based on the contents of aromatic hydrocarbon, aliphatic hydrocarbon and various oxygen-containing functional groups, and designing the structural forms of nitrogen and sulfur; constructing a molecular structure model of lignite.