Abstract: Aiming at a B phase jumper breakage fault on a 35 kV transmission line, the cause of conductor breakage induced by aging of the splice fitting is analyzed through macroscopic inspection, fracture morphology analysis, radiographic testing, and disassembly observation. The results indicate that the line has an operating history of more than 20 years. After long term operation, the conductive grit and adhesive in the inner layer of the preformed splice rods deteriorate and pulverize, leading to poor contact between the splice rods and the conductor and further causing frequent gap discharge. Aeolian vibration and same direction stranding aggravate the wear, resulting in ablation and strand breakage of the aluminum strands. The current transfers to the steel core, initiating a vicious cycle of heating and corrosion, and eventually causing fusing of the steel core and the inner aluminum strands. Based on the fault mechanism, improvement measures are proposed, including special inspection of the same type lines and the promotion of clamp crimping technology to replace preformed splice rods.