Estimation methods of extreme wind speed and turbulence intensity parameters for wind turbine classes recommended by IEC 614001 Ed.3: Wind turbines Part 1: Design Requirements are widely used in wind energy because of its simple and convenient features. Based on the observation data from 193 masts in the professional observation network of wind energy resource in China, we compare the extreme 10 min average wind speeds within a recurrence period of 50 years (V50) by IEC method and extremum Ⅰ distribution which is recommended in China, and obtain the following findings. First of all, there are only 7 masts where the values of V50 by the two methods is relatively consistent within ±1% deviation. Values of V50 by IEC method are generally smaller, and there are 121 masts with V50 lower than -10% and 44 masts with the value lower than -30%, while only 9 masts have the value higher than +10% all around the country. After that, masts with much smaller V50 by IEC method are mainly distributed in southeastern coastal areas affected by typhoon, while masts with small deviations are mainly distributed in the regions with flat terrain in the Northwest and North China, and the masts with deviation over 10% are also concentrated right here. Finally, 46 masts will go into errors if they are calculated only by characteristic indices of the mean turbulence intensity in 15 m·s-1 wind speed, compared to results by the 90% quantile for 15 m·s-1 wind speed.