The diurnal variation characteristics of Aerosol Optical Thickness(AOT) in different city regions and seasons were analyzed by using the long-term measurement data from a sun-photometer DTF in several typical regions of China. It indicates that the AOTs in Chinese different regions show complex and different diurnal variation characteristics and the diurnal variation trend is obviously different. The AOT variations of yearly-mean, monthly-mean, and seasonal-mean in each region were also presented. The results show that the AOT in Lijiang of Yunnan Province is the least, where the atmosphere is clean, and the small particles are dominant, and that in Zhangbei of Hebei Province is the second least one. The AOTs both in Kashi of Xinjiang province and Hefei of Anhui province are larger, and the bigger particles are dominant in Kashi while the smaller particles are dominant in Hefei. In every region, the AOT is larger in spring, and the smallest in autumn. Moreover, the value of AOT is between 0.15 and 0.7 in Kashi, 0.08 and 0.4 in Zhangbei, 0.2 and 0.75 in Hefei, 0.01 and 0.1 in Lijiang, respectively. The frequency distributions of AOT and ngstrm index are basically Gauss distribution. The peak value distribution of AOT from high to low is Hefei, Kashi, Zhangbei, and Lijiang in turn and that of the ngstrm index from high to low is Lijiang, Hefei, Zhangbei, and Kashi in turn.