The utility model relates to a gear hobbing machine rear pillar outer support mechanism which comprises a motor arranged at the top end of a rear pillar, a slide plate which is arranged on side wall of the rear pillar and can slide up and down along a guide rail arranged on the side wall of the rear pillar, and a transmission device which is connected with the motor and used for controlling the slide plate to move up and down. A centre device is installed on the end portion of the slide plate. The centre device comprises a shell body, a centre shaft installed in the shell body, and a centre which is fixedly connected with the end portion of the centre shaft. According to the gear hobbing machine rear pillar outer support mechanism, a rigid matching structure is formed through the centre shaft, a bearing and the shell body to replace a disc spring structure, the position of the slide plate and the pressing force of the centre are controlled through current load, the structure is simple, provided pressing force is stable and reliable, pressing rigidity is better, machining precision is high, and using cost is reduced.