Orthotropic steel deck (OSD) is applied on many bridges around the world, but its drawback of being prone to fatigue has been a concern due to the damages observed. Fatigue cracks initiated from the blunt notch details in rib-to-floor beam connections have a different fatigue behavior compared to welded connections and deserve to be investigated further. To study the effect of notch radius on the fatigue performance of blunt notch detail, 27 specimens with different geometries were manufactured and tested with fatigue loads. The fatigue lives of specimens and their crack initiation locations were investigated, and the prediction on the fatigue life of notched specimens based on the theory of critical distance (TCD) was also conducted. For notched specimens made of S355, the predicted fatigue life using the TCD method is in good agreement with the experimental results. Also, it is found that the point method has higher accuracy compared to the line method and the use of one calibration curve of notched specimens could provide enough accuracy compared to the case when two calibration curves of notched specimens are used. By modifying the mathematical description of the stress distribution near the notch root, a new formulation of the critical distance-fatigue life relationship is here proposed and validated with the experimental results.