The wind speed distribution and Weibull distribution are essential in the assessment of wind resorce. Linear regression is usually used to estimate the Weibull parameters for a wind data. However, it is known that there could be a large error in the estimated Weibull parameters for a wind data of a complex terrain site. The authors believe that a cause of the error is that the wind of a complex terrain has large turbulence component. Actually, the result of analysis showed that a large value of the turbulence intensity caused a large error of the averaged wind speed of the estimated Weibull distribution. This paper gives an example of a relation between the turbulence intensity and the error of the estimated Weibull distribution and a difference in the estimation by some methods.