Supercritical carbon dioxide (SC CO2) extraction of low-concentration ethanol from aqueous solutions was intensified by the addition of salts including inorganic solid salts and ionic liquids. The influence of operating conditions, e.g., the initial aqueous ethanol mass fraction, phase volume ratio, temperature, pressure, and the kinds of salts added on the extraction process was investigated in this work. It was found that KHCO3 is the best among all of the salts investigated, and the salting-out effect of ionic liquids is weaker than that of solid salts. The experimental results are consistent with the Hofmeister series and the prediction of COSMO-RS (conductor-like screening model for real solvent) model. This work also tried to explain the separation mechanism at the microscopic scale. FTIR (Fourier transform infrared) spectrometry and density functional theory were used to explore the complex formation and interaction force of the systems. The pretreatment process could be directly used to detect the prohibited stimulants in athletes or monitor the environmental pollutants at low concentration. This work also opens a new window for the application of ionic liquids and solid salts in sample pretreatment in laboratory rather than only limited in industry.