<p>In order to clarify the initiation and propagation behavior of fatigue cracks in pearlite rail, U76CrRE heavy rail steel samples under three different cooling conditions (production line rolling, production line heat treatment and laboratory heat treatment) were taken as the research object. The fatigue crack growth rate was measured by a fatigue testing machine, and the microstructure, pearlite lamellae, fatigue crack growth trajectory and fracture morphology were observed and analyzed by OM, SEM and EBSD. The results show that the general trend of a-<i>N</i> curves of U76CrRE heavy rail steel under three different cooling conditions is similar, but the fatigue fracture life is 6.7 × 10⁵, 7.5 × 10⁵ and 8.3 × 10⁵ cycles. The crack initiation and entering area I of U76CrRE heavy rail steel of laboratory heat treatment is the most delayed, the fatigue crack growth rate is the slowest and the fatigue fracture life is the longest. EBSD image of crack initiation area shows that the proportion of small-angle grain boundaries of U76CrRE heavy rail steel under three different cooling conditions is 79, 68 and 61% in turn. With the increase of cooling rate, the orientation difference between grains increases and gradually transforms into large-angle grain boundaries, and the grain size is refined, and the interlaminar spacing is reduced, which can reduce the hindrance to dislocation slip and thus inhibit the growth of fatigue cracks. The SEM image shows that with the increase of cooling rate, the fatigue striation spacing and cleavage plane size of fatigue fracture area I and area II of U76CrRE heavy rail steel decrease. The fatigue life of the U76CrRE heavy rail steel of laboratory heat treatment is longer than the other two, which is attributed to the obvious branch crack in the crack growth trajectory of U76CrRE heavy rail steel of laboratory heat treatment, and the energy of crack propagation can be consumed by the branch crack. </p>