The utility model discloses a wire tightening clamp suitable for a 500kV compact power transmission line, which is fixed on a cross arm of the power transmission line, and the cross arm is formed by splicing two angle steel backrests. The clamp comprises a pair of cross arm hanging pieces; the cross arm hanging piece comprises an upper limiting body; Pull rod and connecting rod, The number of theupper limiting bodies is two. The pull rod is perpendicular to the cross arm and arranged above the cross arm in parallel, the upper end of the pull rod is connected with the upper limiting body, thelower end of the pull rod penetrates through the two steel angles of the cross arm, the two ends of the connecting rod are hinged to the lower end of the pull rod respectively, and a U-shaped frame with an upward opening is formed by the pull rod and the two connecting rods. The installation of the clamp on the cross arm does not need a fastener or change the structure of the cross arm, and is convenient and fast. The connecting rod is parallel to the cross arm, and the upper end of the wire tightening adjusting screw rod is connected with the hinge seat of the connecting rod, so that the vertical occupied space is small. After the clamp is installed, an operator can directly tighten the wire on the cross arm as much as possible, so that the operation safety is improved.