A backlight module is provided. The backlight module includes a frame, a plurality of light emitting elements, at least one photo sensor device and a diffusing plate. The frame has a bottom plate on which the plurality of light emitting elements are disposed. The photo sensor device is distributed on the bottom plate and among the plurality of light emitting elements. It is to be noted that the photo sensor device includes a light mixing component having a receiving space configured at a bottom thereof, and a photo sensor chip received in the receiving space. The diffusing plate is disposed in the frame and above the light emitting elements and the photo sensor device. The backlight module has an excellent light outputting performance and an LCD using the same has better displaying performance.