As a critical component of pantograph-catenary systems, the surface physical characteristics of carbon strips directly affect the wear mechanism of friction pairs and current-carrying stability. A ring-on-block high-speed current-carrying tester was employed to investigate the correlation between the surface physical characteristics of carbon strip and its wear mechanisms under sliding speeds of 300 km/h, currents of 300 A, different normal loads, and varying test durations in this study. The evolution of surface roughness was analyzed by using white light interferometry. Results indicate that the surface roughness of carbon strips varies with both increasing normal load and prolonged test duration. Furthermore, the surface roughness of the carbon strips shows a negative correlation with current-carrying efficiency and a positive correlation with wear rate. Analysis of SEM reveals that the wear mechanism of carbon strip varies under different loads. It is worth noting that nodular protrusions appear on the surface of carbon strip under low normal loads, which are transmitted from the contact line. Due to their high hardness, they significantly increase the friction coefficient and surface roughness of carbon strip. The suppression of arc erosion pits and nodular protrusions can effectively improve the contact state of the friction pair, thereby enhancing the current carrying efficiency of the pantograph catenary system and the operational stability of the train.