An optical sensing system and an electronic display system are provided. In the optical sensing system, a light is firstly transmitted to a light guide device via a first light emitting surface and then is transmitted to a light transmissive display screen via a second light emitting surface on the light guide device, and then the light passes through the light transmissive display screen. In this case, even if an area of the first light emitting surface is small due to the small size of an encapsulating body for a light emitting element, energy of the light is not concentrated at a small region of the light transmissive display screen but is dispersed to a relatively large region of the light transmissive display screen, as long as an area of the second light emitting surface is set to be relatively large.