To understand the influence of urbanization process on air quality in urban neighborhood area, the size distribution and seasonal variations of elemental and organic carbon in aerosols were studied at a coastal and suburban site in Xiamen City, China. A total of 87 samples were obtained during the one-year measurement campaign from June 2009 to May 2010. Results indicated that 79.3±3.2% of organic carbon (OC) and 88.3±1.7% of elemental carbon (EC) were associated with fine particles (PM2.5), which consisted of 32.0±8.3% of total carbonaceous aerosol (TCA). The concentrations of OC and EC in PM2.5 were 17.8±11.2 and 3.8±1.9 μg m^-3, respectively, and high concentrations were usually observed as the wind direction was northeastern (NE). High OC/EC ratios (average 5.1) in PM2.5 indicated the formation of secondary organic carbon (SOC), which contributed 60.0% to OC and 11.0% to particulate matter. At this site, SOC had significant negative correlation with temperatures (R²=0.42), and favorable meteorological condition for SOC formation was found in the wintertime. The OC/EC ratios increased with particle size, while the  fractions of carbonaceous aerosol to particulate matter decreased. OC, EC and SOC concentrations and OC/EC ratios followed the same seasonal pattern of winter >spring>autumn>summer, which mainly resulted from the various origins of air masses in different seasons. This study indicated the requirement for mitigating the pollution of carbonaceous aerosol at this coastal and suburban area in Xiamen City.