An oxide semiconductor thin film transistor (TFT) substrate includes a substrate, a source, a drain, a patterned transparent conductive layer, an oxide semiconductor layer, a gate and a gate dielectric layer. The source and drain are disposed on the substrate. The patterned transparent conductive layer includes a first transparent electrode, a second transparent electrode and a pixel electrode. The first and second transparent electrodes respectively cover an upper surface of the source and an upper surface of the drain. The pixel electrode connects to the drain. The oxide semiconductor layer contacts the first and second transparent electrodes. The gate dielectric layer is interposed between the oxide semiconductor layer and the gate.