Abstract: A light source of side-edge type light-emitting diode (LED) backlight unit for using in a liquid crystal display (LCD) comprises a substantial LED bar, at least one primary LED set preset as the light source of the LCD, and at least one backup LED set. The primary LED set(s) and backup LED set(s) are composed of a plurality of LED and disposed at the LED bar, and a backup LED set will be enlightened and substituted for one primary LED set as the light source when the primary LED set is broken-down so that the light source for the LCD is maintained at constant levels.