Abstract: The isothermal transformation curve and continuous cooling curve of U71Mn 75 kg/m heavy rail steel were measured. According to the results of isothermal transformation and continuous cooling transformation, the optimal eutectoid structure in the heavy rail steel could form when the cooling velocity was controlled between 2℃/s and 8℃/s. The comparison tests of U71Mn 75 kg/m steel and U74 60 kg/m steel show that the load capacity of the former is 1.3 times larger than that of the later while the practical fatigue strength is approximate, and the impact toughness of the former is better than that of the later with the same impact force.