The invention relates to a graphite grounding body connecting device for a thunder protective grounding grid of a power transmission line tower. The connecting device comprises a male connecting piece, a female connecting piece and a clamp. The male connecting piece and the female connecting piece are provided with connecting surfaces respectively. Each of the connecting surfaces is provided with an arc-shaped groove in the length direction running through the male connecting piece or the female connecting piece. The bottom of one end of the arc-shaped groove is provided with a U-shaped groove running through the arc-shaped groove and the end acts as an open end. The connecting surfaces of the male connecting piece and the female connecting piece are respectively provided with projections and grooves which are matched. The male connecting piece and the female connecting piece are connected as one connection body through the matching of the projections and the grooves. The arc-shaped grooves on the male connecting piece and the female connecting piece are combined into a hole groove running through the connection body along the longitudinal direction thereof. The graphite grounding body for connection is vertically bended, led in from the open end and led out from the hole groove opening at the other end. The clamp is snapped on the open end side of the connection body and pressed against a bending part of the graphite grounding body. The advantages of the connecting device are: grounding body is not liable to break away from a connecting device; the connection is reliable and easy to construct; long service life is achieved.