A pixel structure and repair method thereof. A through hole is formed in the common line. When the source/drain electrode of a thin film transistor is not electrically connected to a pixel electrode due to a polymer residue remaining in a contact hole, a first laser beam passes through the through hole to weld the source/drain electrode and the pixel electrode. The defective pixel can be thus repaired to display the original color. In addition, if the defective pixel fails due to a defective thin film transistor, the invention irradiates a second laser beam to sever the source/drain electrode such that the defective thin film transistor is not electrically connected to the pixel electrode. The defective pixel can be thus repaired to a dark point.