Supercritical fluid extraction and fractionation (SFEF) has been developed to separate eight Chinese and Mideast petroleum vacuum residua. Elemental analysis, average molecular weight, and SARA (saturates, aromatics, resins, and asphaltenes) determinations were performed on the vacuum residua and their subfractions. Based on an analysis of the collected data, a characteristic index, K-H, consisting of H/C ratio, molecular weight, and density is developed. The index is used to correlate properties such as carbon residue and saturates percentages. The reference data on thermal cracking, catalytic cracking, and heavy oil pyrolysis proved the validity of the new index. Thus, the K-H index is useful in the classification and evaluation of heavy oil and has the potential for extended application.