Inherent damage zone model assumes that σγ0which is the stress at a small distance γ0 from the crack initiation position, governs the fatigue characteristics regardless of the geometric configuration of the specimen. The distance γ0 represents the size of effective Damage zone and it is an inherent length of the material. A special feature of the model is using the exact solution of σγ0. Neuber's analytical solution for notched specimen and Westergaard's stress function for cracked specimen are employed for this purpose. In this paper, the strength of small fatigue crack is investigated based on the inherent damage zone model. A new crack propagation equation which is applicable to both small and large cracks is proposed and the crack propagation property at lower stress intensity factor range is evaluated. Mechanism of non-propagating crack is explained by the comparison of magnitude of σγ0 between crack and notch with the same length. Occurrence condition of non-propagating crack is evaluated for elliptic notches and circular holes. Predicted strength properties of small cracks are in good agreement with the previous experimental data.