Abstract: The 3σ clipping rule is used in a random vibration process in the time-domain and the frequency-domain. In this paper, the frequency-domain methods for the fatigue damage accumulation analysis are used to evaluate the effects of the 3σ clipping rule on the results of fatigue damage accumulation analyses. A narrow-band model described by the Rayleigh distribution and four typical modified approaches is employed to analyze the fatigue influence factors. Numerical simulations show that the fatigue damage accumulation corresponding to the 3σ clipped is only about 70% of the total fatigue damages(with material fatigue parameter m=6). The influence factor analysis based on the narrow-band model can be applied approximately for wide-band random processes.