The objective of this study was to characterize the chemical properties of atmospheric particles sampled in the Kinmen-Xiamen Airshed located on the west bank of the Taiwan Strait. Seven particulate matter (PM) sampling sites in the Kinmen-Xiamen Airshed, including three sites at Kinmen Island and four in urban Xiamen, were selected for this particular study. Regular sampling was conducted to collect PM10 with high-volume samplers twice a month from March 2008, while intensive sampling was conducted to collect PM2.5 and PM2.5–10 with dichotomous samplers and PM10 with high-volume samplers in the spring and winter of 2008–2009. After sampling, the metallic contents of PM10 were analyzed with an inductively coupled plasma-atomic emission spectrometer (ICP-AES). Ionic species and carbonaceous contents of PM10 were analyzed with an ion chromatograph (IC) and elemental analyzer (EA), respectively. Finally, the source identification and apportionment of PM were analyzed by principal component analysis (PCA) and receptor modeling (CMB), respectively. The results from PM10 sampling indicated that atmospheric aerosol particles had a tendency to accumulate in Xiamen Bay all year round, particularly in spring and winter. The five sampling sites at the center of Xiamen Bay had relatively higher PM10 concentrations than the two sampling sites outside Xiamen Bay, suggesting that local emissions from Xiamen Bay were more significant than emissions transported over a long distance by the Northeastern Monsoon. The phenomenon of superimposition was regularly observed during air pollution episodes at Xiamen Bay. Moreover, the results of chemical analysis showed that the main chemical components of the PM were SO42–, NO3–, NH4+, OC, and EC and crustal elements (Ca, Mg, Fe, and Al) in the aerosol particles in the Kinmen-Xiamen Airshed. The neutralization ratios (NR) of PM were generally smaller than unity, indicating that the atmospheric particulates were mostly acidic. The averaged sulfur oxidation ratio (SOR) ranged from 0.20 to 0.51, and the nitrogen oxidation ratio (NOR) ranged from 0.10 to 0.41 for all seasons. The ratios of sulfur and nitrogen oxidation were generally higher than 0.25 and 0.10, respectively, suggesting that secondary sulfate and nitrate aerosols came mainly from across-boundary transportation and could be further accumulated in the Kinmen-Xiamen Airshed. The results from CMB receptor modeling showed that the major sources of atmospheric PM10 in the Kinmen-Xiamen Airshed were soil dusts, secondary aerosols, the petroleum industry, motor vehicle exhausts, the iron and steel industry, the cement industry, diesel vehicle exhausts, marine aerosols, and biomass burning.