Nowadays,　most　photochromic　ferroelectric　materials　strongly　rely　on　thermal　stimulation　to　achieve　color　recovery　after　light　irradiation,　seriously　restricting　their　down-to-earth　application　in　devices.　Here,　we　report　a　sort　of　rare　earth　doped　potassium　sodium　niobate　thick　films,　whose　photochromism　can　be　completely　restored　without　any　external　stimulation.　Through　real-time　monitoring　of　up　conversion　photoluminescence　spectra　and　reflectivity　spectra　after　removing　UV　irradiation,　along　with　the　thermoluminescence　spectra,　a　possible　mechanism　based　on　ion　doping　induced　trap　redistribution　is　proposed.　Generally,　the　emergence　of　intermediate　energy　level　induced　by　rare　earth　ion　doping　is　a　crucial　factor　for　this　spontaneous　behavior.　The　energy　level　depth　of　defects　in　the　thick　films　are　shallower　and　the　trap　distances　are　shorter,　facilitating　the　carrier　transmission　and　recombination　efficiency,　thereby　promoting　the　reversible　self-recovery　process　of　photochromism　at　room　temperature.　Therefore,　an　Er3+　doped　potassium　sodium　niobate　thick　films　with　room-temperature　self-recovery　photochromism　were　prepared,　which　could　increase　the　types　of　potential　photochromic　self-recovery　materials　and　accelerate　the　fundamental　understanding　and　practical　applications.　©　2022　Elsevier　B.V.