The　application　of　halide　perovskite　materials　as　lasing　devices　has　recently　attracted　great　attention.　However,　the　instability　of　such　materials　against　moisture　significantly　restrict　the　application　in　many　occasions.　In　order　to　protect　the　unstable　perovskite　materials　against　oxygen　and　moisture,　various　encapsulation　strategies　have　been　proposed.　Regrettably,　few　of　them　are　designed　for　aqueous　envi-ronments.　Herein,　we　demonstrate　a　photo-polymerized　acrylic　acid　(ADCP)　acting　as　substrate　and　encapsulation　layer　to　fabricate　(CH3NH3)PbBr3　(MAPbBr(3))　films　and　realize　amplified　spontaneous　emission　(ASE)　with　low　threshold　in　water.　Lasing　threshold　from　MAPbBr(3)　films　sandwiched　by　ADCP　decreases　slightly　from　12　mJ/cm(2)　in　air　to　~9　mJ/cm(2)　in　water.　The　specific　morphology,　superb　wettability　and　high-water　stability　are　expected　to　contribute　to　the　low　ASE　threshold.　The　aqueous　environment　with　higher　refractive　index　is　speculated　to　be　one　of　the　origins　of　the　slightly　lower　ASE　threshold.　Our　results　demonstrate　a　strong　potential　for　applications　of　perovskite　materials　in　lasing　devices　in　aqueous　environment　and　a　new　path　to　realize　low　threshold　lasing.　(C)&　nbsp;2022　Elsevier　Ltd.　All　rights　reserved.