A repair method for repairing an active device array substrate is provided. The active device array substrate includes a substrate, scan lines, data lines, active devices, pixel electrodes, and common lines. At least one of the scan line has an open defect. The scan lines and the data lines are intersected to define sub-pixel regions. The active devices are electrically connected with the scan lines and the data lines correspondingly. Each pixel electrode is disposed in one of the sub-pixel regions and electrically connected with one of the active devices. The repair method includes cutting one of the common lines neighboring to the open defect to form a cutting block that is electrically insulated from the common lines; and welding the cutting block, the scan line having the open defect and two active devices located at two opposite sides of the open defect.