Haze phenomena were found to have an increasing tendency in recent years in Yong’an, a mountainous industrial city located in the center part of Fujian Province, China. Atmospheric fine particles (PM2.5) in the urban area during haze periods in three seasons (spring, autumn and winter) from 2007 to 2008 were collected in this study, the mass concentrations and chemical compositions (seventeen elements, water soluble inorganic ions (WSIIs) and carbonaceous species) of PM2.5 were determined. PM2.5 mass concentrations didn’t show a distinct difference among the three seasons. Carbonaceous species of organic carbon (OC) and elemental carbon (EC) constituted up to19.2%--30.4% of PM2.5 mass during sampling periods, while WSIIs occupied 25.3%--52.5% of PM2.5 mass, the major ions in PM2.5 were SO42-, NO3- and NH4+, while the major elements in PM2.5 were Si, K, Pb, Zn, Ca and Al. The experimental results (from data based on three haze periods with a 10-day sampling length each period) showed that the crustal elements species was the most abundant component of PM2.5 in spring, and the secondary ions species (SO42-, NO3-, NH4+, etc) was the most abundant component in PM2.5 in autumn and winter, which indicated that dust was the first pollution source for PM2.5 in spring and combustion and traffic emissions could be the main pollution sources for PM2.5 in autumn and winter. Generally, coal combustion and traffic emissions were considered to be the uppermost pollution sources to this city in haze days.