The invention provides a backlight module and a method for controlling the illumination of the backlight module. The backlight module comprises a plurality of luminous sources, an optical sensor and a control circuit. Each luminous source of the plurality of the luminous sources can be independently operated. The optical sensor is used for detecting the illumination of the plurality of the luminous sources so as to generate a luminance signal. The control circuit is used for driving the plurality of the luminous sources according to the luminance signal. When the backlight module is used for a scanning backlight liquid crystal display, the control circuit closes part of the luminous sources of the plurality of the luminous sources according to a display signal. When the plurality of the luminous sources are all opened, the control circuit reads the luminance signal, and adjusts the illumination of the backlight module according to the luminance signal.