The present disclosure relates to a backlight module. The backlight module is configured for use in a transparent display device and comprises: an optical splitter; and a light source arranged at a side of the optical splitter and emitting light towards the optical splitter. The optical splitter is configured to split light emitted from the light source into a first light beam and a second light beam, wherein the first light beam is configured for supplying backlight, and the second light beam is configured for illuminating background behind the optical splitter. The present disclosure also relates to a transparent display device, comprising the above described backlight module; as well as an array substrate and a color film substrate arranged in front of the backlight module.