An array substrate of a liquid crystal display includes data lines; scanning lines configured to cross with the data lines; a test line provided outside a display region of the array substrate for test of the array substrate; and a repair line provided outside the display region for repair of a defective data line. The test line is configured to be electrically isolated from the repair line when the repair is not carried out and is electrically connected to the repair line and the defective data line when the repair is performed. A method of repairing the array substrate and a liquid crystal display using the array substrate are also provided. According to the invention, the test line can be used as a part of a repair circuit for repair of the data lines, thereby greatly decreasing non-display area.