The present invention discloses a thin-film-transistor array substrate and a manufacturing method thereof. The array substrate includes a thin-film transistor and a compensation electrode. A gate electrode of the thin-film transistor is a portion of a scan-signal line and has an opening, and the opening extends to a side of the scan-signal line. A drain electrode of the thin-film transistor is disposed correspondingly to the opening. A source electrode of the thin-film transistor extends from a side of a data-signal line and surrounds the drain electrode. The compensation electrode extends from another side of the scan-signal line and corresponds to the gate electrode. Therefore, the present invention is capable of reducing parasitic capacitance between the drain electrode and the gate electrode without increasing the resistance value of the scan-signal line.