Abstract: Selection of solvent is the key for extraction to separate n-alkanes from diesels and to improve the flow ability of diesels at low temperature. Sphere model with three-dimensional solubility parameters was applied in the solvent selection. The three-dimensional solubility parameters of n-alkanes in two diesels (atmosphere gas oil and vacuum gas oil) and 11 solvents (chlorinated methane, ketone and ester) are calculated by the group contribution method, and the solvent-solute dissolution judgment (Rs) was thus obtained. The n-alkane precipitation rate (E) was introduced to characterize the deposition efficiency of solvents. The relationship between E and Rs of every kind of solvent was investigated. The results indicate that E increased with the increase of Rs. The linear regression equation between E and Rs is determined. Verified by F-test, the significant linear relationship between E and Rs was found. Therefore, the three-dimensional solubility parameters sphere model can provide the basis for the solvent selection for extraction.