Abstract: The hydro-liquefaction properties of Xiaolongtan (XLT) lignite were investigated, and structures of the heavy products, including asphaltene (AS) and preasphaltene (PA) were characterized by elemental analysis, FT-IR and fluorescence spectroscopy. The results indicate that XLT lignite shows high liquefaction reactivity, and its conversion catalyzed by FeS at 415 ℃ is 89.6%. During hydro-liquefaction, the macro-molecule of coal are pyrolyzed and deoxygenized. The aromatic structure units in AS and PA are similar to those in the coal. Hydroxyl and carbonyl in the form of aromatic ketone are main oxygen containing groups in AS and PA. The relative content of aromatic structure of PA, dominant in the archipelago molecular architecture, is obviously higher than that of AS. In THF solvent, PA shows significantly stronger aggregation than AS, especially an intra-molecular aggregation observed in a dilute solution. The AS and PA produced at high liquefaction temperature contain more aromatic structure, and show stronger aggregation.