Abstract: In order to ensure wind turbine running safely and steadily in complicated environment, a probabilistic model for analysis of the failure of a wind-turbine rotor blade in flap-wise bending is presented. This model capitalizes on stress-strength interference theory and curve, and Weibull model about the wind's distribution is considered. This model accounts for the uncertainties about the loads acting on the wind-turbine rotor blade by the unstable wind distribution. A 20-year design lifetime is assumed. The probability of fatigue failure in flap-wise bending of the rotor blade is calculated by means of a first-order reliability method. Four situations are calculated when turbulence intensities are 0.02, 0.1, 0.15, 0.2 and wind velocity is 12 m/s.Conclusions can be draun through comparison:linearity of Gumbel distribution is better than one of three-parameter Weibull distribution and Weibull distribution, because the two distributions have some tails. At last, Stress-strength Interference Theory model is validated by 600 kW wind turbine blade.Conclusion has chown that wind turbine rotor blade can meet the design standards.