The invention relates to an automatic stripping device for an outer sheath of a high-voltage cable. The automatic stripping device comprises a base, wherein a fixed rod and a screw rod are respectively, vertically and fixedly arranged at an edge side of the base, a stripping support sleeves the fixed rod and can vertically move, a motor is arranged on the support, is capable of speed change and direction adjustment and is connected with a rotation shaft vertically arranged, the rotation shaft is connected with the screw rod via a group of power gear set so that the stripping support can vertically move, the rotation shaft is further arranged on the stripping support via a group of striping gear set, a cable channel is formed in the middle of the stripping support, comprises a steering gear in a vertical direction and is used for a cable to insert and rotate with the cable channel in a clamping way, the motor is arranged at the upper part of the stripping support, the lower part is connected with the rotation shaft vertically and laterally arranged at the screw rod, the power gear set comprises an upper power transmission gear and a lower power transmission gear which are fixed on the rotation shaft, and each of the power transmission gears is engaged with a power gear engaged on the screw rod via an internal tooth hole.