A problem of the air pollution control in China is getting to know a regional contribution rate of internal and external source of PM_(2.5). In this paper,Set Pair Analysis( SPA) method is proposed to calculate the contribution rate of PM_(2.5)in Dongguan City. Due to geographic,meteorological factors and the low concentration of air pollutants in Qingxi area,the PM_(2.5)in this place is mainly contributed by the regional transport of air pollutants from other inside areas of Dongguan,and less affected by the outside of Dongguan. So the concentration of PM_(2.5)in Qingxi area can reflect the Dongguan's basic background concentration of PM_(2.5). On the basis of the basic background concentration,firstly the concentration of each pollutant components is divided into the internal part and the mixed part. Secondly using the source apportionment samples of five monitoring sites in Dongguan we can respectively construct a sample set A and an evaluation set B. Thirdly the SPA is operated onto the mixed part in terms of set B.At last the connection degree between the concentration of each pollutant components and external source and internal source will be calculated,that is the contribution rate. The research reveals that the contribution rate of internal source and external source of PM_(2.5)in Dongguan City is 83%and 17% respectively,which roughly met expectations. This method is simple and effective and it can provide a reference for the government taking reduction measures to control PM_(2.5)pollutants emission.
