Based on the relationship between the sea surface roughness (z0) and the 10 m wind speed, a method is developed for the 10 m wind speed in this paper. By comparing with the ERAInterim wind speed, a very good correlation is obtained. And the wind speed calculated by this method is closer to the ERAInterim wind speed than the speed by the fixed z0 method. Based on this dynamic z0 method, the data from two weather stations on the offshore oil platform in the South China Sea is used to calculate the hourly 10 m wind speed and the corresponding dynamic roughness length for nearly four years. The analysis reveals the wind speed ranges mainly within 3-13 m·s-1. The average wind speed is smaller from April to September and larger from October to March. The daily variation of wind speed has the following characteristics in 14:00-17:00 BT, the wind speed is at the minimum and in 06:00-09:00 BT, the wind speed reaches the maximum. In addition, there is significant seasonal variation and daily variation of z0 value which is consistent with the variation of wind speed. The variation of meteorological elements is analyzed when the center of Vicente passed the station, and the result shows that the corrected wind speed and z0 are in accord with the actual observation values.