The paper presents a methodology for reliability analysis of a modem large wind turbine blade considering stochastic wind loading.A 5-MW wind turbine blade, which has been developed by National Renewable Energy Laboratory (NREL), is utilized as the blade model to be studied.In order to better render the chaotic characteristic of a random wind field, the wind uncertainty has been represented by two random variables, the mean wind speed and turbulence intensity factor.By statistically studying measured wind velocity data, the distribution of 10-min mean wind speed in one year is validated to be a Weibull distribution;and the distribution of 10-min turbulence intensity factor is found to best fit a log-logistic distribution.