Atmospheric aerosol (PM10) samples were collected at Xiamen from December 2004 to July 2005, and analyzed by XRF、IC and Carbon Analyzer . Concentrations of aerosol species were commonly highest in spring, second highest in winter, and lowest in summer. Secondary ions including SO42-、NO3-, and NH4+ accounted for about 40% of PM10, and total carbon, crustal elements such as Al、Si、Ca and Fe , salt ions accounted for about 21%, 13%,, and 7%, respectively, of the PM2.5 mass. Secondary ion pollution is the major contributor to Xiamen air quality.