Abstract: Objective: Causes for serious arc pulling, abnormal wear and collapse of pantograph carbon strip at Guangzhou Metro Line 9 operation early stage need to be identified, so that improvement measures can be proposed and train operation can be less affected. Method: The possibility of poor material and train vibration inducing carbon strip abnormal wear is excluded from the aspects of vehicle state and catenary state. On this basis, the location of pantograph detachment points is identified, and it is discovered that arc pulling is serious when pantograph passes expansion element. By analyzing the speed data of MVB (multifunction vehicle bus), the main line signal mileage mark and carbody data, the expansion element of the main line catenary is accurately located, and it is found that the pantograph will produce great vibration when it passes through the expansion element and the pantographcatenary matching is poor at this point. Furthermore, the topic of carbon strip abnormal wear is communicated with peers in China and the reason of pantograph carbon strip abnormal wear is concluded. Result & Conclusion: Expansion element structure problem is the main cause of pantograph carbon strip abnormal wear. Optimization measures include optimizing the transition segment length and transition mode of expansion element auxiliary line, optimizing expansion joint layout, and optimizing train traction software. By adopting the above measures, pantographcatenary relation is obviously improved, manifested as a significant extension of carbon strip service life, a great decrease in traction failure rate and train maintenance costs.