The fatigue curve or S-N curve shows the relation of the stress and the cycle number and could be used to predict lifetime. The S-N curve is estimated from fatigue data of the test using the constant cyclic stress amplitude. This article presents a study of tensile fatigue tests with constant and ramping stress amplitudes to estimate the S-N curve of steel material. The fatigue test with ramping stress amplitude overcomes disadvantages of the test with constant amplitude. The two testing methods were performed on the steel specimens newly designed and analyzed to see whether the S-N curve of steel could be estimated by using the parameters obtained from the ramping test. Although the amount of data is still small, the results suggest that this hypothesis is feasible.