Abstract: Annual average diffusion coefficient of each city was estimated according to ①annual SO2emission from high,middle and low chimneys in the key environmental protection cities,based on data from countrywide pollutant emission reporting and registry,②annual SO2 average concentration given by Chian's Environmental Quality Report of 1996,and ③relationship between the pollutant emissions from chimneys of different heights and the surface environmental quality.Based on these estimates,the cities were classified into for categories,i.e.unfavorable,comparatively unfavorable,comparatively favorable and favorable to pollutant diffusion.This method can guide the design of total amount control options for SO2 emission.