The present disclosure provides a thin film transistor (TFT) substrate and a display device, the TFT substrate includes an base substrate and a plurality of pixel units, wherein each of the pixel units includes a TFT on the base substrate, the TFT includes a source drain layer, an active layer, and a gate layer; the TFT substrate further includes a light shielding layer on a side of the source drain layer of the TFT distal to the base substrate, and an orthographic projection of the light shielding layer on the base substrate completely covers an orthographic projection of the active layer of the TFT on the base substrate, and partially covers an orthographic projection of the gate layer of the TFT on the base substrate.