Abstract: The effects of hydrothermal treatment on the structure and hydroliquefaction property of Shenhua coal were studied by determination of maximum reflectivity of vitrinite and TG analysis of treated coal. In addition, TG/DTA and IR characterizations were also used to compare the structure of preasphaltenes obtained from liquefaction products of raw coal and hydrothermally treated coal. The results indicate that maximum reflectivity of vitrinite from treated coal is higher than that of raw coal and increases with the hydrothermal treatment temperature. For 250℃ hydrothermal treatment coal, the vitrinite maximum reflectivity is 0.774 % and the weight loss is higher than that of other treated coal. The effects of hydrothermal treatment on hydroliquefaction properties of treated coal are in accord with the influences on vitrinite maximum reflectivity and thermogravimetric property. Hydrothermal treatment of coal under optimal temperature can improve the pyrolysis and cyclization of aliphatic side chain in coal macromolecular, the ability of donation hydrogen, and increase the vitrinite maximum reflectivity so that the liquefaction reactivity of the treated coal is improved. In addition, the thermal stability of preasphaltene from liquefaction products of treated coal is also distinctly enhanced compared to that of raw coal.