A system for backlight detection using the brightness values of the subareas in a focus area and method therefor are provided, which are applicable to an image capture device. The focus area is divided into a plurality of subareas and the brightness values of each of the subareas are calculated. Then, the brightness values of each of the subareas are converted into 0 and 1 codes, and then the codes are combined to generate the codes representing the entire focus area. The status values corresponding to each of the codes are determined with reference to a backlight detection table established in advance, so as to determine whether an object to be shot is in a backlight condition.