Abstract: The suspension clamp on the right side of the double circuit tangent tower of a 500 kV transmission line broke, causing the ground wire and OPGW optical cable to drop. The cause of the suspension clamp fracture was analyzed by stereo microscopy, optical microscopy, automatic hardness tester, scanning electron microscopy. The results showed that the fastening bolts of the suspension clamp were corroded seriously, and the aluminum alloy material of the metal fitting sheath was unqualified.There was abnormal tempered sorbite on the surface of the bolt wear area, which indicated that the bolt had experienced high temperature. Comprehensive analysis showed that, poor continuity and open circuit caused by ground wire corrosion were the root causes of the abrasion and fracture of the clamp sheath.