The solvent oil comprises a cutting fraction and a refining process of two. The cutting distillate process usually has the following three ways: direct cutting from the atmospheric pressure Tower, the corresponding light straight distillate cut into appropriate narrow fractions, and the catalytic reforming of the residual oil fractionation. A variety of solvent oil fractions are generally required to undergo refining processing. To improve color, stability, removal of corrosive substances and reduce toxicity. The common refining methods include alkali washing, white clay refining and hydrofining.