Abstract: Richardson number's stability classifying schemes of the surface layer over the coastal region are analyzed by using the data obtained from two 100m towers located on the coastal area of Guangdong and Zhejiang provinces. Based on the wind speed, temperature, and wind direction data obtained at 10, 25, 50, 75, 100m,it is found that the limits of stability classes of the routine Richardson number classifying schemes were not available for the coastal region. A new Richardson number classifying schemes limit of the coastal region is proposed.