Abstract: The cathodic protection system of a certain gas company's pipeline adopted an impressed current cathodic protection method with the flexible anode as the auxiliary anode bed. The cathodic protection system had some problems such as severe fluctuations in output voltage and protection potential, low output current and high output voltage, as well as low output current and output voltage. In response to the above issues, the investigation revealed that the cathodic protection system failed due to factors such as subway stray current interference and flexible anode cable breakage in the pipeline. The results show that changing the distribution of the anode bed, adding cathodic protection systems, and adding anti-interference probes at the power point could effectively restore the normal operation of the cathodic protection system, enabling pipelines to achieve effective cathodic protection status.