The invention discloses an automatic clamping device for a high voltage grounding wire. The device is characterized in that an upward single-side rack upper wire clamping block is arranged on a connecting block and passes through a single-side rack; a six-rod mechanism comprises three connecting frame rods and two connecting rods; the three connecting frame rods are distributed from top to bottom on the connecting block; the first connecting frame rod, the second connecting frame rod and the corresponding first connecting rod form a parallelogram movement pair which drives the first connecting rod to move up and down by reciprocating; a lower wire clamping block directly adopts the first connecting rod as a connecting block or is connected to the first connecting rod; the lower wire clamping block and the upper wire clamping block are equipped with clamping surfaces which are parallel to each other; a connecting device which can be connected with an insulating operating rod is arranged on the second connecting rod which is connected with the second connecting frame rod and the third connecting frame rod; a stopping device is arranged between the third connecting frame rod and the second connecting rod. With the adoption of the device, an efficient clamping torque can be provided, so that a ground wire can be mounted according to the standard; meanwhile, the labor intensity of operators in ground wire mounting can be greatly reduced, and the working efficiency can be increased.