The fatigue crack propagation of heavy rail steel has a very complex relationship with the stress and strain at the crack tip, but there is currently little research on this mechanism. This article takes pearlite heavy rail steel as the research object under three conditions (increasing cooling rate): online rolling state, online heat treatment state, and laboratory heat treatment state. The pearlite layers at different cooling rates were observed using scanning electron microscopy, and the tensile fatigue crack and stress field cloud map at the crack tip of the heavy rail steel were measured using fatigue testing machines and strain gauges. Then, a stress and strain model was established based on Abaqus, the results indicate that as the cooling rate increases, the interlayer spacing of pearlite decreases; With the fatigue crack propagation, the stress field strength around the crack and the Stress intensity factor k at the crack tip increase, and the stress field is more significant in the "butterfly" shape. The Stress intensity factor of the laboratory heat treated heavy rail steel at the crack length of 1, 2, 3 mm is 13.53, 14.58, and 15.54 MPa·m^1/2, respectively, which is far greater than that of the rolled and heat treated heavy rail steel at the same crack length; As the fatigue crack length increases, the equivalent strain area near the crack tip increases. At the same crack length, the equivalent strain at the crack tip of three kinds of heavy rail steels with cooling rate decreases with the decrease of pearlite lamellae. The simulation results of equivalent strain at a longer crack length of 3 mm are 0.074, 0.067 and 0.055 respectively, while the strain experimental results are 0.082, 0.064 and 0.058 respectively. The maximum error between the simulation results and the strain field experimental results is 5.1%, which verifies the model. Both simulation and experimental results show that the smaller the pearlite lamella is, the larger the Stress intensity factor at the crack tip is during the fatigue crack growth process of heavy rail steel, the smaller the equivalent strain area is, the stronger the fracture resistance is, and the better the fatigue performance is.