The paper studies influence of the second-highest loads in variable-amplitudeloading on fatigue crack 8rowth (FCG)through experiments with 16 Mn steel compact tension speci-ments, The reaults show that the second-highest loads decreasc the retardation effect of the highestloads on FCG ,and the closer to highest load in value the second-highest loads, the greater the de-creasing in the retardation effect. The effect of the second-highest loads can explain the great differ-ence betwcen the constant-amplitude loading with singl-peak-overload and random loading in FCG rates.