The invention provides a cross arm for an electric power circuit. According to the technical scheme, the cross arm comprises two cross arm bodies fixed to a tower. The two ends of the two cross arm bodies are fixedly provided with two longitudinal arm bodies. The cross arm is characterized in that the inner sides of the two cross arm bodies are each provided with a first clamping ring matched with the tower, the cross arm further comprises second clamping rings matched with the tower and located below the cross arm bodies and the longitudinal arm bodies, the bottoms of the two longitudinal arm bodies are each hinged to a pull rod, and the other ends of the pull rods are in sliding connection with the second clamping rings. By adjusting the cross arm, the cross arm is in the balanced state and can be firmly fixed to the tower, maintenance is performed by workers conveniently, and the electric leakage accident caused by the cross arm is reduced.