Abstract: Good correlated equations about molecular weight has been selected with the experimental data for petroleum fractions from distillation and other processing. Related equations for boiling points, carbon numbers and characteristic factor K were regressed from the informations of a large number of pure hydrocarbon compounds. Petroleum fractions were considered to be broken down into carbon number pseudocomponents. In this paper, they were further characterized by determining their molecular weight, characterized factor K, sulfur and nitrogen contents and mole and carbon number flow rate in addition to the aromatic carbon, naphthenic carbon and paraffinic carbon fractions. These charaterization steps were presented and compared. These rusults can be applied for predicating properties of various products in kinetic modelling of hydrogenation and other processes.