Abstract: An event of ablation of disconnector contacts caused by corrosion is analyzed. The c-phase closing switch of a 220 kV line is not in place. Due to the insufficient corrosion resistance of the three-phase connecting rod, the transmission is stuck. The resulting heating develops gradually under the action of positive feedback, and finally leads to contact ablation. This paper analyzes the process of the accident and summarizes that the cause of heating is the problem of material and technology. There is electrochemical corrosion between the crank arm, joint material and copper sleeve. Some measures such as carrying out temperature rise test and analyzing and verifying the margin of conductor insertion depth are put forward as the basis for following works.