Abstract: An analysis was conducted on the fatigue crack growth between last disc and blade of a domestic 600 MW steam turbine using software ABAQUS, so as to study the stress distribution in that area and the crack propagation in the rim with maximum stress. Considering the effect of fluctuating steam load on the rim fatigue crack, the growth law of fatigue crack in the rim with maximum stress was simulated respectively at the rated speed of 3 000 r/min and the overspeed of 3 300 r/min, thus to find the relationship between the number of crack growth cycles and the length of end surface cracks, and to compare the crack length under two working conditions after 1±10⁶ cycles. Results show that the crack tends to grow more easily under overspeed condition, and the propagation rate is also higher than that under rated condition.