Abstract: The paper presents a method to determine hydrocarbon types of aromatic fraction from residue by high ionizing voltage,low resolution MS. the asphaltenes in the residue samples were precipitated using n-heptane. The heptane-soluble components were further fractionated into saturates,aromatics and resins on the alumina/silica gel column. Then the aromatic fractions were analyzed on a VG Autospec mass spectrometer with a HP5890 GC. All glass heated inlet system was used to vaporize the sample into the gaseous phase. the mass spectrometric data were processed using group-type methods. the calculations were carried out to sum the relative abundance of characteristic peaks of each class,and each summation of peaks indicates corresponding hydrocarbon type. The analyses show that the vaporizing temperature has little impact on the composition at certain temperature ranges and the tests produce highly repeatable results.