Abstract: To investigate the variation of air pollution and the relationship of the variation and its influence factors in Beijing and Shanghai,the atmospheric pollution characteristics and variety pattern of primary atmospheric pollutant in Beijing and Shanghai in 2004 and 2005 were analyzed according to the monitoring data of ambient air quality.The results showed that the maximum concentration of PM10 was 637 times greater than the minimum in Beijing in 2004 and 2005;the variation range of PM10 concentration in Beijing was larger than that in Shanghai.The maximum concentration of SO2 was 467 times greater than the minimum value in Beijing in 2004 and 2005,the maximum concentration of SO2 was 131 times greater than the minimum in Shanghai with the variation range smaller than that in Beijing.The concentrations of NO2 were relatively large and had not obvious season variations.The annual daily mean concentration of NO2 in Beijing and Shanghai met the second level of the national ambient air quality standard（NAAQS）.The annual daily mean concentration of SO2 in Beijing in 2004~2005 and Shanghai in 2004 met the second level，whereas that in Shanghai in 2005 slightly exceeded the second level.The serious SO2 pollution in Shanghai related with the combustion of plentiful coal;the smart variation of SO2 concentration in a year in Beijing was related with the combustion of coal for heating in winter.The pollution of inhalable particulate matter (PM10) in the two cities was serious.The annual daily mean concentration of PM10 in Beijing in 2004,2005 exceeded the second standard level of NAAQS，and that in Shanghai met the second level of NAAQS at the same periods.On the whole，the ambient air quality of Shanghai was better than that of Beijing.The temporal variation pattern of top pollutants in Beijing and Shanghai were related with various factors such as pollutant sources,geography,climate,etc.

Key words: characteristics of atmospheric pollution, inhalable particulate matter (PM10), SO2, NO2, Beijing City, Shanghai City