PM_2.5 samples were collected in Sanming,Fujian province from March 13 to April 20,2014.The mass concentrations were determined and the chemical characteristics were analyzed by thermal optical carbon analyzer and ion chromatography.During the observation period in Sanming city,the average mass concentration of PM_2.5 was 73.61±0.73 μg/m³.The averaged value of organic and elemental carbon were respectively 7.26±1.00 and 5.63±0.27μg/m³,and the mass concentration fraction of four ions,including SO₄^2-(18.08±12.19μg/m³),NH₄⁺(4.18±3.56 μg/m³),NO₃^-(2.77±1.16 μg/m³) and Na⁺(2.73±0.23 μg/m³),accounted for 87.76% of total water-soluble ions.Moreover,backward trajectory analysis indicated that the major pollution sources were located to the southeast of Sanming.The average ratio of OC to EC was 1.89,which is less than 2,indicating that there was little SOC production in atmospheric fine particles in Sanming city,while the primary organic pollutants were dominating the PM_2.5 pollution.The correlation between K⁺ and OC,EC demonstrated that OC,EC have the similar source with K⁺,therefore we concluded that the primarysource of pollutants was biomass burning.The mean result of NO₃^-/SO₄^2- was 0.159±0.02,indicating that stationary sources were the dominated contributor whilemobile sources such as motor vehicle contributedmuch less.