The invention discloses a back wall illumination system of an elevator, which comprises an illumination lamp, wherein the illumination lamp is mounted on a back wall of an elevator car; a routing hole allowing a lead wire to pass through is formed in the back wall; one end of the lead wire is connected with the illumination lamp; and the other end of the lead wire is connected with electrical equipment at the upper part of the elevator car. According to the illumination system, the illumination lamp is mounted on the back wall of the elevator car, so that the illumination lamp is easier to mount, dismount and maintain, ascending is not required when the illumination lamp mounted on the back wall is maintained, and the repair efficiency of the illumination lamp is improved obviously. In addition, the routing hole is formed in the back wall and used for allowing the lead wire to be connected with the electrical equipment; with the adoption of the routing hole, the lead wire is not required to be exposed in the elevator car, and the safety of passengers and attractiveness of the elevator car can be ensured.