In　this　paper,　GdFeO3　thin　films　with　high　orientation　and　heavily　Ce3+　doping　were　deposited　by　radio　frequency　magnetron　sputtering　with　a　matching　substrate.　The　effects　of　substrates　and　Ce3+　doping　on　the　structure,　magnetic　and　magneto-optical　properties　of　thin　films　were　investigated.　As　a　result,　Ce3+　doping　can　not　only　increase　the　saturation　magnetization　but　also　greatly　enhance　the　magnetic　circular　dichroism　signals　of　Ce:GdFeO3　thin　films.　Based　on　the　density　functional　theory　calculation,　it　can　be　found　that　the　probability　of　electron　transition　between　Ce3+　4f　and　Fe3+　3d　and　the　difference　in　the　absorption　of　right　and　left　circularly　polarized　light　increase,　which　results　in　the　strong　magneto-optical　effect　of　Ce:GdFeO3/STO　thin　films.