Methyl　iodide　(CH3I)　gas　as　a　toxic　gas　causes　great　harm　to　organisms　due　to　its　high　volatility　and　high　reactivity　with　biological　nucleophiles.　Unfortunately,　the　sensing　and　detection　of　CH3I　gas　are　challenging　because　of　the　diffusive　nature　of　the　gases　and　its　low　concentrations　in　the　environment.　Herein,　we　have　developed　a　fast,　green,　and　sensitive　CH3I　gas　visual　sensing　method　based　on　the　capture　technology　of　toxic　gases　by　natural　deep　eutectic　solvents　(NADESs)　coupled　to　the　halide　rapid　exchange　capability　of　perovskite　nanocrystals　(PNCs).　In　this　strategy,　NADESs　are　used　as　an　absorption　solution　to　adsorb　gaseous　CH3I,　while　simultaneously　exposing　I-　through　the　action　of　the　nucleophilic　reagent;　then,　CsPbBr3　PNCs　were　synthesized　in　NADESs　and　used　as　sensing　material　to　achieve　I-　exchange.　Benefiting　from　the　capture　and　enrichment　of　CH3I　gas,　the　sensitivity　of　the　gas　sensor　was　highly　improved.　The　sensor　exhibited　the　lowest　detection　limit　(limits　of　detection)　of　164.15　mu　mol/m(3),　below　the　minimum　safe　level　for　human　inhalation,　which　is　200　mu　mol/m(3).　This　breakthrough　offers　greater　possibilities　for　the　quantitative　detection　of　CH3I　gas.