The work aims to investigate the effect of load on surface microstructure and property of D2 wheel steel under sliding wear. The sliding wear tests were conducted on the MRH-30 sliding wear machine. The microstructure evolution, surface wear morphology and micro-hardness at different depth from surface after sliding wear under different load conditions were analyzed withanoptical microscope, a field emission scanning electron microscopy, an X-ray diffractometer and a field emission transmission electron microscopy. The weight loss of the wheel and rail samples increased gradually with the increase of sliding wear time. After certain sliding wear time, the weight loss of the wheel sample under 200 N condition was higher than that of the wheel sample under 100 N condition. On the contrary, the rail sample under 200 N condition exhibited better wear resistance. After sliding wear, the rod-like white etching layer (WEL) and the discontinuous crescent-shaped WEL were formed at the wheel sample surface under different load conditions. In WEL, the lamellar cementite was dissolved obviously and ferrite grains were refined, whose size was about 100 nm. The thickness of the WEL of the wheel samples increased with sliding wear time increasing under different load conditions. However, the thickness of WEL under 200 N condition was thinner than that under 100 N condition after different sliding wear time owing to high weight loss. The micro-hardness of the WEL was high due to the dissolution of a large amount of cementite and the formation of nano-ferrite grains. The surface hardness of the WEL under 200 N condition was lower than that under 100 N condition. In WEL, the hardness showed a gradient from the surface to the plastic deformed layer. High weight loss reduced the thickness of the WEL, thus resulting in the decrease of surface hardness in WEL under 200 N condition. The discontinuous crescent-shaped WEL was more likely to form at the wheel sample surface under 200 N condition. Due to the existence of asperity on the wheel and rail sample surface, high load could accelerate the severe plastic deformation of local asperity on the wheel and rail sample surface, resulting in the formation of discontinuous crescent-shaped WEL. The discontinuous crescent-shaped WEL signification affected the wear property of the wheel sample.During sliding wear process, under 200 N condition, the cracks were easy initiated at the interface of discontinuous crescent-shaped WEL and the microstructure surrounding discontinuous crescent-shaped WEL. Moreover, the cracks also were easy to propagate at the interface of crescent-shaped WEL and the microstructure surrounding crescent-shaped WEL gradually, causing the flaking of discontinuous crescent-shaped WEL. The flaking of discontinuous crescent-shaped WEL could increase the wear loss of the wheel sample. When the discontinuous crescent-shaped WEL was flaked, the difference of hardness between the wheel sample and the rail sample further was expanded. The wheel sample wear was further accelerated during sliding wear process. On the other hand, high load could accelerate plastic deformation in no WEL area to cause the ratcheting failure and then accelerate the wear failure of the wheel sample.