A thin-film transistor (TFT), a manufacturing method thereof, display substrate and a display device are disclosed. The TFT includes: an active layer, gate insulating layer, gate electrode, interlayer dielectric layer, source electrode and a drain electrode disposed on a base substrate in sequence. The source electrode and drain electrode are respectively connected with the active layer via a through hole exposing the active layer; the gate insulating layer at least includes a silicon oxide layer and a silicon nitride layer in a two-layer structure; the interlayer dielectric layer at least includes silicon oxide layers and silicon nitride layers in a four-layer structure; the silicon oxide layers and silicon nitride layers of the gate insulating layer and the interlayer dielectric layer are alternately arranged; and the dimension of one side of the through hole away from the base substrate is greater than that of one side close to the base substrate.