Light-emitting　lead　halide　perovskite　materials　have　attracted　great　attention　due　to　their　excellent　optoelectrical　properties.　However,　the　combination　of　perovskites　and　conjugated　polymers　forming　an　exciplex　has　not　been　reported　due　to　the　limitations　of　fabrication.　In　this　work,　we　introduce　a　strategy　by　using　an　ultraviolet　(UV)-polymerizable　acrylic　monomer　to　fabricate　perovskite-polymer　composite　films　in　the　polymer　matrix.　Significantly,　we　systematically　examined　the　exciton　dynamics　in　composite　films　by　time　resolved　photoluminescence　and　transient　absorption　spectra.　We　observed　the　formation　of　an　exciplex　and　the　emission　from　it.　The　energy　levels　and　exciton　dynamics　of　perovskite　light-emitting　polymers　in　the　composite　is　proved　to　be　influenced　by　the　photopolymer　matrix　and　the　energy　levels　in　the　polymer　matrix　make　the　charge　transfer　and　exciplex　formation　feasible.　Furthermore,　light-emitting　devices　were　fabricated　using　the　composite　materials　as　phosphors　on　a　395　nm　UV　chip.　The　devices　illustrate　excellent　water-repellent　properties,　which　can　work　in　an　aqueous　atmosphere　for　a　long　time.　This　method　provides　a　facile　strategy　for　the　preparation　of　ultrastable　composites　employing　both　perovskites　and　light-emitting　polymers　and　deepens　our　understanding　of　the　exciton　dynamics　in　such　composite　materials.　It　is　beneficial　for　the　development　of　next-generation　light-emitting　devices　and　displays.