A dynamic analysis method is proposed for evaluating the structural strength of large excavators. The method is validated by employing a heavy mining shovel. The front-end is created as a flexible multi-body dynamics system using Lagrange equations and finite element technology. The model loadings are constructed from the machine motion, operation, and inertia. The variable amplitude stress ranges are recovered from structural dynamics simulation, and then are transformed to equivalent constant amplitude stress range with the rainflow counting method and Palmgren-Miner's cumulative damage rule. The result comparisons from the simulation with the measured field data and static analysis show that the dynamic analysis gives a higher safety confidence in the shovel front-end stress simulation than the static analysis. The validated model is used to predict the longevity of shovel structural components. The derived analysis method can be applied to any mining excavators for the fatigue life prediction.