A thin film transistor (TFT) substrate includes a substrate and a TFT. The TFT is disposed on the substrate and comprises a gate, a gate dielectric layer, a film, a source and a drain. The gate is disposed on the substrate. The gate dielectric layer is disposed on the gate and the substrate. The film is disposed above the gate dielectric layer, and the source and the drain are disposed on the film and contacts with the film respectively. Wherein, there is an interval between the source and the drain, and the film corresponding to the interval has an arc concave portion. In addition, a display panel is also disclosed.