Abstract: Natural fatigue crack growth (NFCG) has been investigated extensively for decades due to its significant influence on the overall life of key components and the complex mechanism involved. In this study, a NFCG model based on the phenomenological observations of fatigue crack growth is first invoked, and a computational strategy is developed in the scaled boundary finite element method (SBFEM) context to simulate the NFCG phenomenon and to predict the fatigue life of specimen with different thicknesses under various cyclic loading conditions. The effects ascribed to the loading conditions, specimen thickness and material properties on the NFCG can be investigated in detail with the our elaborated strategy, which provides a helpful tool for practical specimen design, material selection and eddy current testing.