Abstract: A gas transmission pipeline was affected by the subway interference. The pipeline cathodic protection potential fluctuated greatly and was positive than -850 mV(compared to CSE) for a long time. As a result, the cathodic protection system was seriously interfered, and the effect of cathodic protection on the pipeline was unknown. In order to know the real cathodic protection status of the pipeline, the soil resistivity was tested, and the pipeline potential were monitored for 24 hours, so as to determine the minimum cathodic protection potential value and evaluate the cathodic protection status of the pipeline. Based on the corrosion risk analysis results, the cathodic protection station running parameters were adjusted and continuous feeding tests were carried out. Through continuous field test, an optimized interference protection method was obtained.