Deep　eutectic　solvents　(DESs)　are　a　class　of　promising　media　for　gas　separation.　In　order　to　examine　the　potential　application　of　DESs　for　natural　gas　upgrading,　the　solubilities　of　H2S,　CO2,　and　CH4　in　choline　chloride　(ChCl)　plus　urea　mixtures　were　measured　in　this　work.　The　solubility　data　were　correlated　with　Henry＇s　law　equation　to　calculate　the　thermodynamic　properties　of　gas　absorption　processes,　such　as　Henry＇s　constants　and　enthalpy　changes.　Grand-canonical　Monte　Carlo　simulations　and　quantum　chemistry　calculations　were　also　performed　to　examine　the　mechanism　of　gas　absorption　processes.　It　is　found　that　the　absorption　of　H2S　in　ChCl　+　urea　mixtures　is　governed　by　the　hydrogen-bond　interaction　between　Cl　of　ChCl　and　H　of　H2S,　whereas　the　absorption　of　CO2　and　CH4　in　ChCl+urea　mixtures　is　governed　by　the　free　volume　of　solvents.　Based　on　the　different　behavior　of　gas　absorption,　high　H2S/CO2,　H2S/CH4,　and　CO2/CH4　selectivities　can　be　achieved　by　adjusting　the　ratio　of　ChCl/urea　in　mixtures.　©　2019　American　Institute　of　Chemical　Engineers