Abstract: 4 bituminous coals with different ranks were thermally and hydrothermally treated under different conditions, and the raw and treated coals were extracted with carbon disulfide/N2pyrrolidinone (CS2/NMP) mixed solvent (1∶1 by volume). It is found that the extraction yields of the thermal or hydrothermal treated coals at proper conditions increase in different extent. The increments of extraction yields for hydrothermal treated coals are higher than those of thermal treated coals. FTIR shows that the adsorption peaks at 3410 cm－1 attributed to OH group for the hydrothermal treated coals decrease, suggesting the dissociation of the coal aggregation structure due to the breakage of hydrogen bonds, resulting in the increase of extraction yields for the treated coals. For higher rank coal, the removal of minerals and the dissociation of π cation association after hydrothermal treatment of coal may be responsible for the increase of extraction yield. In addition, the mechanism of hydrothermal treatment of coal was discussed.