Taking a turbine runner blade under hydraulic excitation as the object of this study, the fluid-structure interaction dynamic model of the runner blade was established using the finite element method, and the vibration characteristics and the dynamic stress characteristics of the runner blade have been explored. Based on this, the characteristics of vibration and fatigue of the turbine runner blade were then analyzed using the Pairs fatigue crack growth model, and the fatigue crack growth regularity of the runner blade under hydraulic excitation was discovered. The influence of a fatigue crack on the ultimate strength of a runner blade was then discussed according to the strength theory, and the dynamic characteristics of the ultimate strength of a runner blade under the influence of vibration fatigue have been revealed. Finally, the dynamic characteristics of the ultimate strength of a turbine runner blade under hydraulic excitation were simulated and analyzed using an example from the literature. The results showed that the ultimate strength of turbine runner blades was not only related to their vibration characteristics but also their fatigue characteristics. It was found that with the propagation of a fatigue crack in a runner blade, its ultimate strength decreased continuously.