A thin film transistor, comprising: a source electrode over a substrate; a first insulation layer having a source contact through-hole corresponding to the source electrode over the source electrode; an active layer electrically connecting with the source electrode through the source contact through-hole over the first insulation layer; a second insulation layer having a drain contact through-hole exposing an upper surface of a portion of the active layer disposed outside the source contact through-hole; and a drain electrode electrically connecting with the active layer through the drain contact through-hole over the second insulation layer, wherein the thin film transistor further comprises: a gate in a layer the same as that the drain electrode is located, with the gate and the drain electrode being made of a same metal material layer, an orthographic projection of the gate on the substrate at least partially overlapping with an orthographic projection of the source electrode on the substrate and the gate being over the second insulation layer, or a gate in a layer the same as that the source electrode is located, with the gate and the source electrode being made of a same metal material layer, the orthographic projection of the gate on the substrate at least partially overlapping with an orthographic projection of the drain electrode on the substrate, the gate being over the substrate and the first insulation layer being over the gate. a source electrode over a substrate; a first insulation layer having a source contact through-hole corresponding to the source electrode over the source electrode; an active layer electrically connecting with the source electrode through the source contact through-hole over the first insulation layer; a second insulation layer having a drain contact through-hole exposing an upper surface of a portion of the active layer disposed outside the source contact through-hole; and a drain electrode electrically connecting with the active layer through the drain contact through-hole over the second insulation layer, wherein the thin film transistor further comprises: a gate in a layer the same as that the drain electrode is located, with the gate and the drain electrode being made of a same metal material layer, an orthographic projection of the gate on the substrate at least partially overlapping with an orthographic projection of the source electrode on the substrate and the gate being over the second insulation layer, or a gate in a layer the same as that the source electrode is located, with the gate and the source electrode being made of a same metal material layer, the orthographic projection of the gate on the substrate at least partially overlapping with an orthographic projection of the drain electrode on the substrate, the gate being over the substrate and the first insulation layer being over the gate. a gate in a layer the same as that the drain electrode is located, with the gate and the drain electrode being made of a same metal material layer, an orthographic projection of the gate on the substrate at least partially overlapping with an orthographic projection of the source electrode on the substrate and the gate being over the second insulation layer, or a gate in a layer the same as that the source electrode is located, with the gate and the source electrode being made of a same metal material layer, the orthographic projection of the gate on the substrate at least partially overlapping with an orthographic projection of the drain electrode on the substrate, the gate being over the substrate and the first insulation layer being over the gate.