The solubility parameter(δ≡△E/V)1/2 means the cohesive energy density of the composed molecule. In the themodynamic mixing theory, if both the solute and solvent have the same or close δ value, they will be spontaneously mixed together. So it can be used as an index for solvent selection. For the δ measurement of hydrocarbons, either single component or its heavy cuts, the following two methods can be applied well including LCO and asphaltene: (1) From the relationship of δ and α Watson characterization factor K δ = 15.89 – 0.68 K (2) The relationship of δ and H/C δ = 10.89-1.60H/C