| Aerosol optical depth (AOD) were obtained by using the vapor pressure and the visibility data over 70 stations in China in January, April, July, October from 1981 to 2003, then the statistical characteristics of aerosol optical depth were analyzed. And the relativity of aerosol optical depth and visibility were analyzed, as well as its impact on the air temperature.It is found that: (1) The yearly-mean AOD has typical spatial character. There is a maximum in the Sichuan Basins for the yearly mean AOD. The largest AOD centers are located in the Sichuan Basin and the medium downstream of Yangtze River, while the second largest one is located in Guangdong coastal area. In reverse, AOD is lower in the Yunnan-Guizhou Plateau, northwest and the northeast of China. The distribution of AOD for each month is similar to yearly-mean AOD, but it has the annual variation, national AOD great value area scope reduces at first and then increases from January to October. (2)The maximum AOD in different parts of China occurs in different season. Based on the seasonal variety of AOD in each station, it can be divided into three types. They are peak type, valley type and a form of unimodal undulace. (3)From 1981 to 2003, the national average AOD shows increasing trends in some stations, such as Nanjing, Hangzhou, Hefei and etc. By contrast, it shows reducing trends in other stations like Maduo, Wuhan, Tianjin, Shenyang, Lanzhou, and so on. And the trends in other stations like Changsha, Xining, Aletai, Lijiang, and Datong are not obvious. The yearly average AOD shows maximum values in 1992, 2002. (4) The monthly mean aerosol optical depth has a strong correlation with surface visibility's reciprocal, and the correlation in different seasons is obvious different in which it shows the worst relationship in spring. AOD and visibility's reciprocal linearity fitting varies with the seasons, the largest value occurs in spring. (5) The wintertime temperatures in Sichuan Basin respond to the AOD to some extent.
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