In　this　work,　a　mixed　absorbent　of　an　ionic　liquid　(IL)　and　triethylene　glycol　(TEG)　is　first　proposed　for　natural　gas　(　NG)　dehydration.　The　hydrophilic　[EMIM][BF4]　is　selected　as　an　appropriate　IL　composition　from　240　potential　candidates　by　calculating　the　thermodynamic　separation　factors　(i.e.,　solubility　and　selectivity).　The　separation　mechanism　of　NG　dehydration　with　the　mixed　absorbent　of　[EMIM][BF4]　+　TEG　at　the　microscopic　molecular　level　is　systematically　unraveled　by　employing　the　COSMO-RS　model　and　quantum　chemical　calculations.　The　solubility　of　CH4　in　pure　[EMIM][BF4]　and　TEG,　as　well　as　in　binary　mixtures　of　[EMIM][BF4]　+　H2O　and　[EMIM][BF4]　+　TEG,　is　experimentally　measured　and　predicted　by　the　modified　(mod.)　UNIFAC-Lei　model.　It　is　proved　that　the　mod.　UNIFAC-Lei　model　can　well　predict　the　gas-liquid　equilibrium　(GLE)　and　be　successfully　extended　from　binary　to　ternary　systems.　In　the　dehydration　experiment,　the　mixed　absorbent　shows　an　excellent　dehydration　performance　(i.e.,　the　water　content　of　the　product　gas　is　decreased　to　172　ppm,　in　mole　fraction).　The　equilibrium　(EQ)　stage　model　embedded　with　the　mod.　UNIFAC-Lei　model　parameters　is　built　to　carry　out　the　process　simulation　of　CH4　dehydration　at　the　laboratory　and　industrial　scales.　The　results　show　that　the　total　annual　cost　(TAC)　of　the　optimized　process　with　mixed　solvents　is　reduced　by　33.63　and　15.98%,　respectively,　at　the　same　separation　conditions　when　compared　to　that　of　pure　TEG　and　pure　IL　processes.　This　confirms　that　the　IL-based　mixed　absorbent　is　a　promising　alternative　to　pure　ILs　or　conventional　solvents　for　applications　in　the　field　of　gas　separation　and　purification.