Abstract: A large amount of arc was generated during the breaking process of a SF₆ circuit breaker. Under the action of arc heat and a large amount of ultraviolet radiation, the external and internal of polytetrafluoroethylene were very easy to generate conductive carbides, which reduced the insulation performance of the arc extinguishing nozzle and greatly reduced the mechanical properties of the arc extinguishing nozzle. In order to improve the ablation resistance of the nozzle, a method of filling blue cobalt aluminate CoO-Al₂O₃ in the nozzle of self-energy arc extinguishing chamber was proposed. The mixing method and molding process were analyzed. The results show that this method could improve the mechanical properties of the nozzle and reduce the loss of arc ablation.