Xilingol No. 6 lignite (XL) was subjected to thermal dissolution in methanol at 200 degrees C, 240 degrees C, 280 degrees C, and 320 degrees C, respectively. Each reaction mixture was sequentially extracted with methanol and isometric carbon disulfide/acetone mixed solvent in a modified Soxhlet extractor to afford extracts a and b, respectively. According to the analysis with a Curie-point pyrolyzer-gas chromatograph/mass spectrometer, the main products from the flash pyrolysis of E-a320, i.e., E-a obtained from XL methanolysis at 320 degrees C, are phenolic compounds. The analysis with a quadrupole-orbitrap mass spectrometer indicates that N3O2-N3O4 are predominant nitrogen-and oxygen-containing class species (NOCCSs) in E-a320. In the NOCCSs, nitrogen atoms mainly exist in the forms of pyridine, imidazole or pyrazole, and pyrazine or pyrimidine, while the main oxygen atoms exist in alkoxy, furan, ester or carbonyl group. In addition, possible pathways for the formation of the NOCCSs were speculated.