The molecular structure model of the Shengli lignite was determined via TG-GC/MS for the analysis of the pyrolysis products' structure and contents, in combination with ultimate analysis and FTIR for the determination of its structure parameters. Then the model was constructed by hand referring to references, optimized and revised on the basis of quantum chemistry by semi-empirical and the second derivative force field. It was estimated that the cross-links were comprised of ether bond (-O-), aliphatic bond (-CH2-, -CH2-CH(2)A), ester bond, -S-S-, etc., and heterocyclic compounds were mainly furan, indole, quinoline, etc., while its oxygen-containing functional groups were primarily carboxyl, hydroxyl, and ether. The molecular formula for the lignite structure model was C169H140O44N3S2. A FTIR spectrum calculated based on the model is consistent with that of the experimental data. (C) 2017 Elsevier Ltd. All rights reserved.