Abstract: According to the observations measured in low troposphere of Guangdong for five years,the characteristics of frequency distribution of Pasquill stability for different areas and its diurnal,seasonal and annual changes were analysed. The results indicate that the neutral frequency appears to be the maximum for Pasquill stability in the whole of Guangdong and the values of unstable (A─C) frequency are higher than those of stable (E─F) frequency. The values of neutral frequency decrease in the order of the coastal area,plain and mountainous area while the values of unstable and stable frequency increase in the same sequence.