Abstract: The expert system is used to analyze and predict the cities where acid rain once took place according to the seven kinds of data of 114 cities of China in 1995, namely the emission of SO2, NOx, CH4, the and NH3, average annual temperature, the average annual precipitation, and the pH of soil. As Compared with the pH experimental value of the 114 cities in 1993-1995, only the prediction results of nine cities are wrong, the total rate of error being less than 8%.