A thin film transistor array substrate and a manufacturing method thereof are provided. Wherein, scan lines and data lines are disposed on a substrate to define a plurality of pixel regions. Thin film transistors are disposed in the pixel regions correspondingly and driven by the scan lines and the data lines. Pixel electrodes are disposed in the pixel regions respectively and electrically connected to the corresponding thin film transistors. In addition, a gate insulating layer is disposed on the substrate to cover the scan lines and gates of the thin film transistors. A patterned leaning layer is disposed on the gate insulating layer and forms a plurality of non-continuous patterns under the data lines. The non-continuous patterns expose portions of the gate insulating layer under the data lines to which a portion of each data line can be directly attached.