Abstract: Thermal dissolution behaviors of Shengli (SL) and Xiaolongtan (XLT) lignite in methanol were investigated. The composition and structural characteristics of soluble portions (SPs) obtained at 320 ℃ were characterized with Fourier transform infrared spectroscopy, gas chromatograph /mass spectrometer (GC/MS) and atmospheric solid analysis probe/time of flight mass spectrometer (ASAP/TOF-MS). For the two lignites, the yield of SPs increase with temperature increasing, while the yield of SPs from XLT (SP_XLT) is obvious higher than that from SL (SP_SL) above 240 ℃. GC/MS analysis results show that compounds in the SPs are dominated in oxygen-containing organic species, especially the relative content of phenols is higher than 49%. The relative contents of alkenes, arenes, ethers, carboxylic acids, esters, organosulfur compounds (OSCs) in SP_SL are higher, while the relative contents of alkanes, phenols, ketones and organonitrogen compounds in SP_SL are lower than those in SP_XLT. Additionally, the OSCs in SP_SL and SP_XLT are mainly composed of thiophenes and mercaptan, respectively. Many compounds with high polarity and low volatility which could not be identified by GC/MS were identified using ASAP/TOF-MS. The relative contents of CHO and CHS class species in SP_SL are higher, but the relative contents of CHN, CHNO, CHOS, CHNS and CHNOS in SP_SL are lower than those in SP_XLT. The carbon number and double bond equivalent (DBE) of the compounds in SP_SL and SP_XLT mainly distribute in 0-10 and 3-15, respectively, while the distribution of carbon number and DBE of the compound in SP_XLT are more concentrated than those in SP_SL.