Passive　daytime　radiative　cooling　(PDRC)　has　been　widely　used　in　environmental　protection,　energy　conservation　and　cooling.　However,　most　PDRC　designs　primarily　focused　on　improving　the　daytime　cooling　effect　while　ignoring　the　problem　of　nighttime　overcooling.　Here,　we　designed　a　flexible　and　multifunctional　composite　film　doped　with　rare　earth　phosphors,　which　has　high　solar　reflectivity　and　high　infrared　emissivity.　During　the　daytime,　it　realizes　subambient　cooling　of　approximate　to　11　degrees　C　at　an　average　solar　radiation　density　of　827.74　W　m-2.　Remarkably,　it　addresses　the　problem　of　nighttime　overcooling　by　maintaining　a　minimal　temperature　difference　of　only　0.5-1.5　degrees　C.　Moreover,　the　rare　earth　phosphors　doped　in　our　design　not　only　effectively　compete　with　titanium　dioxide　nanoparticles　for　ultraviolet　absorption　during　the　day,　but　also　exhibit　significant　luminescence　at　night,　providing　a　useful　color　reminder　effect.　These　findings　highlight　the　exceptional　properties　of　the　radiative　cooler　and　promote　its　applications　in　a　variety　of　fields.　Flexible　composite　films　based　on　rare　earth　phosphors　can　be　used　as　broadband　thermal　emitters　for　passive　radiative　cooling　and　energy　conservation.