Abstract: Because of rolling contact fatigue damage, heavy-load railway frog parts cracked or fractured for several times. In the present work, the physical and chemical properties of the white structure at the fatigue damage area were characterized and analyzed with optical microscope, scanning electron microscope, energy dispersive spectrometer and micro-hardness tester. The results show that the microstructure of the white structure is nanoscale fiber texture, and there is no significant difference in chemical composition between the white structure and the matrix. There is a transition zone with a width of about 3.4 μm between the white structure and the matrix. The hardness of the white structure can be as high as HV 1165, and its high hardness is related to the strength of the material itself and the cycle number of loading. With the rise of the material strength or the cycle number of loading, the hardness of the white structure increases.