The　chlorine　(Cl2)　drying　technology　using　ionic　liquids　(ILs)　as　absorbents　was　proposed　for　the　first　time　and　systematically　investigated　from　the　molecular　level　scaled　up　to　the　industrial　level.The　hygroscopic　IL[EMIM][CH3SO3]was　screened　as　a　suitable　absorbent　from　238　potential　IL　candidates　consisting　of　14　cations　and　17　anions,by　calculating　the　Cl2　and　H2O　solubility　and　separation　selectivity　of　Cl2　to　H2O　in　different　ILs　based　on　the　COSMO-RS　model.The　microscopic　atomic　and　molecular　insights　into　the　separation　mechanisms　were　deeply　revealed　by　using　COSMO-RS　model　analyses　(i.e.,σ-profiles,σ-potentials,excess　enthalpies,entropies,and　Gibbs　free　energies)　and　quantum　chemistry　calculation　(binding　energies　and　weak　interaction　analyses).The　Cl2　solubility　in　pure　IL　and　H2O　+　IL　systems　were　predicted　by　the　COSMO-RS　model,and　the　results　agree　with　the　microscopic　mechanism　identification.Moreover,the　strict　equilibrium　stage　model　employed　with　the　COSMO-RS　model　parameters　was　built　to　perform　the　process　simulation,and　continuous　Cl2　drying　with　ILs　was　conceptually　designed　and　optimized　at　industrial　scale.It　was　confirmed　that[EMIM][CH3SO3]is　a　very　promising　absorbent　leading　to　a　less　IL　amount,a　much　lower　energy　consumption　than　the　other　IL[EMIM][BF4],which　has　a　very　bright　industrialization　potential　used　for　Cl2　drying　technology.