Abstract: LED could be used for both the illumination and the wireless communication simultaneously that owns the modulation bandwidth from several MHz to several hundreds of MHz. The criterion of the minimum mean square deviation was used to design the layout of LED in the room. The indoor illumination distribution was analyzed in the two conditions which were respectively not included the wall reflection and included it. Then the illuminance, the received power for detector and the signal to noise ratio for the line of sight(not including the wall reflection) and the non line of sight(including the wall reflection) were analyzed, respectively. It is concluded that the illuminance and the received power are larger for the non line of sight than the line of sight, but the signal to noise ratio decreases. This is mainly caused by the inter symbol interference from the reflection of the wall of the non line of sight.