The invention relates to a thin film transistor, which comprises a semiconductor layer, a source, a drain, a gate and an insulation layer, wherein the source and the drain are arranged at an interval; the semiconductor layer is electrically connected with the source and the drain; the gate is arranged in an insulation mode with the semiconductor layer, the source and the drain via the insulation layer; the semiconductor layer is an oxide semiconductor film; the oxide semiconductor film contains an Indium (In) element, a Cerium (Ce) element, a Zinc (Zn) element and an oxygen element (O), and the molar ratio of In to Ce to Zn is 2 to 0.5-2 to 1; and the oxide semiconductor film is an n-type semiconductor, carrier concentration is 10<12>cm<-3> to 10<20>cm<-3>, and carrier mobility is 5.0cm<2>V<-1>s<-1> to 45.0cm<2>V<-1>s<-1>. The invention also relates to a thin film transistor preparation method, a thin film transistor panel and a display device.