The effects of ΔK-gradient and cyclic loading below ΔK_th on characteristics in fatigue crack growth were investigated under ΔK-increasing tests. In this study, specimens were annealed in vacuum after precracking, thus the precrack could be regarded as an ideal crack. The results show that the ΔK-gradient, namely C=1/ΔK·dΔK/da, is a controlling factor to fatigue crack growth. When C is sufficiently large, the crack growth rates are accerelated, because the contribution of the fretting oxide induced crack closure are reduced. Cyclic loading below ΔK_th influences on the following crack growth characteristics for the case of low stress ratio, R=0.05. However, the effect disappears for R=0.85 Therefore, ΔK-increasing tests should be carried out under high stress ratio and C value. In this test method, non-oxide controlled crack growth characteristics can be obtaind much more rapidly than in the conventional ΔK-decreasing test under R-constant condition.