Abstract: Supercritical pentane extraction and fractionation was used to separate Dagang vacuum residue into 16 fractions and a nonextractable endcut. The narrow fractions were characterized by composition and average molecular structure. Furthermore, the narrow fractions were separated into the saturate, aromatic, resin and asphaltene. Their composition, molecular weight distribution and average molecular structure were also studied in detail. The properties of saturate, aromatic, resin and asphaltene show many differences, such as simpler molecular structure of the saturates， lower molecular weight of the aromatics， more sulphur and nitrogen contents of the resin， wider molecular weight distribution from 200 to 40000 of the asphaltene.