The invention discloses an ultrathin backlight module and an aligning structure thereof. The aligning structure comprises a mounting block and a carrier plate, wherein the mounting block is used for fixing an LED (Light Emitting Diode) light source; the carrier plate is used for carrying a light guide plate; the mounting block comprises a first base plate and a first lateral plate which are vertical to each other; the first base plate is glued with the carrier plate; a blocking slot and a plurality of through holes are formed on the first lateral plate; the blocking slot is penetrated along the length direction of the first lateral plate; the through holes are penetrated through the bottom of the blocking slot; the through holes are linearly arrayed along the extending direction of the blocking slot; one end of the light guide plate is accommodated in the blocking slot; and LED beads of the LED light source are penetrated into the through holes and face to the blocking slot. The invention also discloses a display device. According to the invention, the carrier plate is utilized to carry the light guide plate, the mounting block used for fixing the LED light source is arranged on the carrier plate and the mounting block is designed as a unique structure into which the LED beads and the limiting light guide plate are simultaneously penetrated, so that the LED light source and the light guide plate are in higher aligning precision and the display quality of the ultrathin backlight module and the display device is also guaranteed.