Abstract: Based on the fatigue crack growth experiments of hypereutectoid rail under different stress ratios, the effects of stress ratio on the crack growth rate of hypereutectoid rail were studied. The fatigue cycles of 8 ℃/s and rolled hypereutectoid steel were compared when the stress ratio increases. The influence of thermal treatment on the sensitivity of hypereutectoid rail to stress ratio was analyzed. The results show that the stress ratio is the main external factor affecting the fatigue performance of hypereutectoid rail, and the heat treatment can reduce the influence and sensitivity of the change of stress ratio on fatigue crack growth to a certain extent. The fatigue cycle number of rolled hypereutectoid rail increases by 53,100 cycles,and the fatigue cycle number of hypereutectoid rail by 8 ℃/s cold quenching process increases by 146,400 cycles; at the sameΔK, with the increase of stress ratio, the fatigue crack growth rate increases. When the stress ratio R increases from 0.1 to 0.3,the cycle times of the hypereutectoid steel rail in 8 ℃/s cold quenching process increase by 93,300 cycles compared with that of the rolled hypereutectoid rail.