The surface crack growth rate and characteristics under high stresses cyclic loading were investigated using SN490B structural steel. It has been found that the crack growth rate under the elastic-plastic and general yielding condition was expressible as the power function of the range of J-integralΔ J. The main results obtained were as follows. (1) The shape of the cracks changed the semi-circular one into the semi-elliptical one according to the cracks propagated under the load and/or deformation controlled condition respectively. (2) TheΔ J values given by three estimation methods of J-integralΔJ-ΔJaeq, ΔJw, ΔJφ-were almost equivalent respectively. (3) The surface crack growth rate was able to estimate by the through-thickness crack growth one by mean of convert the surface crack into the through-thickness one. In this case, there were limitations of the applicability which were σnet<sf, c/t<0.8, a/W<0.5, and da/dN<2×10-4m/cycle.
