Comprehensive　Summary　Organic　room-temperature　phosphorescence　(ORTP)　materials　have　attracted　widespread　attention　in　the　fields　of　OLED,　optical　imaging　and　sensors.　Herein,　we　successfully　prepared　a　long　afterglow　IPA-MA　crystalline　films　using　iso-phthalic　acid　(IPA)　and　melamine　(MA)　by　a　simple　drop-casting　layer-by-layer　(LBL)　method,　which　achieved　an　ultra-long　emission　lifetime　of　up　to　1.15　s.　The　drop-casting　LBL　method　is　effective　for　the　fabrication　of　hydrogen　bonded　supramolecular　crystalline　film　materials　on　solid　surfaces.　The　structure　of　the　IPA-MA　crystalline　film　materials　is　consistent　with　that　grown　by　hydrothermal　method.　Importantly,　this　method　eliminates　the　high　temperature　and　high　pressure　conditions　of　conventional　hydrothermal　methods　and　could　form　supramolecular　crystalline　thin　films　very　well.　In　addition,　the　films　have　great　long　afterglow　performance　and　the　afterglow　time　can　be　controlled　by　altering　the　number　of　film　layers.　Furthermore,　this　method　is　successfully　applied　in　the　fields　of　temperature　sensors　and　anti-counterfeiting.　These　results　not　only　provide　the　foundation　for　the　design　of　organic　long　afterglow　films,　but　also　expand　the　application　fields　of　ORTP　materials.