The commonly used production process of paraffin from feedstock oil is solvent dewaxing, so it is very important to find out thethermodynamic basic data of feedstock oil in organic solvent and the crystalline morphology of wax crystals.The solubility of hydrofining of3rd vacuum side-cut foots oils obtained from Fischer- Tropsch synthesis (i.e. vacuum distillate) in Toluene, Methyl isobutyl ketone, 2Butanone, 2-Propaol and 2-Butanone-Toluene mixed solvents (3 ∶ 1) were measured by a dynamic method.The results show that the sol⁃ubility of the vacuum distillate in those 6 solvents all increases with the increase of temperature, with the greatest solubility in toluene andthe lowest solubility in 2-Propaol.The modified Apelblat equation, simplified Van′t Hoff equation and Polynomial equation were usedto correlate the experimental solubility data.The results indicate that the solubility data can be well correlated by these three models,andthe obtained model equation can predict the solubility of vacuum fractions in 6 solvents within the measured temperature range, with thebinomial equation fitting the best. The dissolution Gibbs energy, dissolution enthalpy and dissolution entropy of the binary system ofvacuum distillate oil and organic solventwere obtained on the basis of the modified Van′t Hoff model and the experimental data. The resultsshow that the dissolution process of vacuum distillate in the studied solvents is an endothermic and non-spontaneous process, and the con⁃fusion of the system increases during the dissolution. The morphology of wax crystals crystallized in 6 solvents were observed with a polari⁃zing microscope.The results show that the wax molecules precipitated to form flake crystals with short-range ordering. The wax crystalshave the largest radial dimension in the 2-Butanone-Toluene mixed solvents, but still not exceeding 50 μm. the wax crystals precipitate in2-Butanone-Toluene and Methyl isobutylketone have larger radial size and better deoilization effect.