Abstract: After processing the visibility data inhomogeneity from inconsistent record formats before and after the year 1980, the authors obtain the long-term time series of visibility, from which the time series of atmospheric aerosol optical depth over China during 1960 to 2005 is derived. It shows well consistency with former observations and researches on long-term variation of aerosol optical depth over China. It is found that the aerosol optical depth over China showed an increasing trend but a slow upward trend after 1985, especially in the megacity regions. The aerosol optical depth is small in northwestern China and large in southeastern China where the aerosol optical depth is generally greater than 0.4, and the maximum of more than 0.8 is located in the Sichuan Basin.