A backlight assembly has an improvement on the structure for eliminating the gap between a light guide plate and a light source. The improvement includes a flexible printed circuit consisting of a body and a mount portion at each of its two ends. The mount portion has a substantially V-arm with a coupling hole. A mold frame has two couplers at its front surface and close to the coupling holes of the flexible printed circuit. The distance between the two coupling holes is substantially smaller than the distance between the couplers for generating deformation force. Consequently, when the two couplers are engaged with the coupling holes, the light source will be attached close to the light incident edge of the light guide plate, thereby eliminating the gap between the light guide plate and the light source.