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This paper investigated the causes of premature wear of grounding brushes in high-speed train which was less than 40 % of design service life. The grounding brushes were analyzed from the material composition, microstructure and mechanical property under different wear conditions. The results indicated that their material composition and microstructure were basically identical, and the phase compositions of the four samples were mainly copper (Cu) and carbon (C). There were no obvious defects in the structure. The load differences will give rise to vibration of the friction pairs and lead to electrical erosion on the worn surface. The electrical erosion produced oxides and fused hard particles as well as caused abrasive wear. The test results also indicated that the spring-induced gap across the contact surfaces resulted in electrical erosion. Keywords:High-speed train / grounding brush / abrasive wear / spring-induced gap / electrical erosion Schlüsselwörter: Hochgeschwindigkeitszug / Erdungsbürste / abrasiver Verschleiß / federinduzierter Spalt / Elektroerosion