This study is concerned with the estimation of wind load factors in the major cities reflecting the recent meteorological with largest data samples(yearly 1971-2010, daily 1990-2010). The basic wind speeds were standardized homogeneously to the surface roughness category C, and to 10m above the ground surface. This study uses the de Haan method for the basic wind speeds, which were found in previous studies to perform about as well or better than the other methods. The analyses provide persuasive evidences that extreme wind speeds are described predominantly by reverse Weibull distribution, which unlike the Gumbel distribution has finite upper tails. This study seeks to ascertain whether the Korean Building Code-Structural(KBCS) is an appropriate estimation method of wind load factors by performing probabilistic analyses for knowledge uncertainties based on the reliability principles and by Code method in the treatment of wind load factors.