Abstract: External corrosion direct assessment method was applied to PX transportation pipeline External Corrosion Testing. The buried pipeline testing consisted of environmental investigation, soil corrosion detection, cathodic protection testing and detection of anticorrosive coating. The testing results were rated. In the detection of anticorrosive coating, C-scan was applied to test coating insulation resistance, and Pearson method and the close-interval potential survey(CIPS) were used to determine coating damage point. The excavation confirmed that the combination of detection methods was effective. Efficient and accurate new method was provided for underground leak detection of pipeline coatings.