Abstract: Daily PM_2.5 samples were collected from January to November of 2015 in Guangzhou. Mass concentrations of organic carbon (OC) and elemental carbon (EC) were determined by the means of thermal/optical reflection (TOR) methods. The results show that the annual average concentration of PM_2.5 was (69.5±35.6) μg·m^-3 which is two times that of secondary standard limits of the latest national standard GB 3095-2012 (Ambient Air Quality Standard)(35 μg·m^-3), suggesting serious PM_2.5 pollution in Guangzhou. The annual average concentrations of OC, EC, total carbonaceous aerosols were (8.31±4.53), (3.56±2.72), (16.85±9.60) μg·m^-3, with their proportions of 13.2%, 5.9%, 27.0% to PM_2.5 mass concentrations, respectively, indicating that carbonaceous species were important components in PM_2.5. The differences of seasonal variation were observed between OC and EC. The OC highest concentration was observed in winter while EC highest concentration was in autumn. Poorer correlations and higher ratios of OC and EC indicated that the most serious secondary organic carbon (SOC) pollution was in winter. The SOC concentration in winter was 6.9 μg·m^-3, accounting for 62.4% of OC concentration. Source apportionment results of principle component analysis (PCA) show that the sources of carbonaceous components were complex in winter and spring and the main sources were vehicle exhausts, coal combustion and biomass burning, while the dominated sources in summer were coal combustion and vehicle exhausts, and the dominated source in autumn was vehicle exhausts.