Abstract: Current ambient air quality assessment system could not comprehensively reflect the pollution status of complex air pollution in Jiangsu Province and had big disparity with the public perception, in which SO₂, NO₂ and PM₁₀ were targeted for control as the major pollutants. By analyzing the PM_2.5 pollution status and sources in Jiangsu Province, summarizing the results of epidemiological and toxicological studies on the effect of ambient air PM_2.5 on human health, and combing the analysis of foreign ambient air quality standards for PM_2.5, it was suggested to involve PM_2.5 in the ambient air quality index system in Jiangsu, and to establish ambient air quality standards for PM_2.5 suitable to the air pollution characteristics as well as the economic and technological level of Jiangsu Province.