The crack growth threshold, ΔKth, for the short crack at the root of a long notch including the effects of notch root radius, ρ, and stress ratio, R, were investigated in this study. The pre-crack, with a depth of 0.15mm, was introduced at the root of a 2mm deep notch which had the root radius changed from 0.015mm to 15mm. A crack propagation test using the unloading elastic compliance method was carried out with the stress ratios of -1, 0 and 0.62-0.72 (high R). The material was normalized 0.25 % carbon steel. The change in ΔKth with the change in ρ was dependent on R. Under R = -1, there was a reduction in ΔKth when the notch root radius was greater than 0.5mm. On the other hand, for R = 0 and high R, ΔKth was almost constant regardless of ρ. Although ΔKth was different depending on the stress ratio and notch root radius, the effective crack growth threshold (ΔKeff)th was constant under all the test conditions. Therefore, the change in the crack growth behavior of the short crack at the notch root was dominated by the crack closure. The reduction in ΔKth in the relatively dull notch for R = -1 could also be explained by the change in the development of the crack closure during crack growth.