Ionic liquids (ILs) were proposed as promising separating agents for the hydrofluorocarbons (HFCs) pentafluoroethane (R125) dehydration. Taking into account the H2O solubility and selectivity of H2O to R125 in a variety of IL candidates, we determined the hydrophilic [EMIM][BF4] as a satisfactory absorbent. Besides, some theoretical insights into separation mechanism at the molecular level were explored by means of the combination of COSMO-RS model and quantum chemistry calculation. The gas liquid equilibrium (GLE) data for the binary R125-[EMIM][BF4] and ternary R125-H2O-[EMIM][BF4] systems were measured, and the experimental data were compared with the predicted results by COSMO-RS model. The R125 dehydration experiment with IL was carried out. Furthermore, the continuous processes for R125 dehydration with [EMIM][BF4] and the conventional benchmark solvent tetraethylene glycol (TeEG) as absorbents were simulated and optimized with the rigorous equilibrium (EQ) stage model, in which COSMO-SAC model was selected. It was confirmed that the R125 gas dehydration with IL presented in this work is a typical process intensification technology.