An auxiliary device for mounting a current transformer of a middle-arranged switchgear comprises the components of an elevator, a supporting platform, a vertical sliding table, a transverse sliding table, a turntable and a positioning unit. According to the specific mounting environment of the middle-arranged switchgear and the moving direction of a current inductor in actual operation, quick feeding and micro feeding adjustment in a vertical surface to a current inductor mounting screw hole relative to the threaded hole position in assembling maintenance are realized. Transverse feeding motion, longitudinal feeding motion and rotation motion in the horizontal surface are realized. A requirement for realizing correspondence between the current transformer threaded hole and the assembling threaded hole of the middle-arranged switchgear is satisfied through adjusting feeding in multiple directions and rotation alignment of the auxiliary device and placing the current transformer on the turntable in the mounting process. Lifting of the current transformer through manpower is not required, thereby reducing labor intensity; improving assembling reliability; shortening time length in mounting, maintenance and replacement; and shortening power-off maintenance time.