Water soluble organic carbon (WSOC) makes up a large fraction of organic carbon, which attracted great attention due to its light absorption properties and human health effects. Sources and light absorption properties of WSOC in 10 cities across China were studied by dual carbon isotope analysis and UV−visible spectrophotometer, respectively. Despite the dominate contribution of non-fossil sources, the fossil sources contribution of WSOC in China was higher than other regions across the world. The average MAE365 and fossil sources contribution of WSOC was 1.13 ± 0.37 m2/gC and 39.9 ± 9.4%, both of which were higher in Northern China. The non-fossil sources contribution of WSOC and MAE365, WSOC exhibited significant seasonal variations with highest values during cold seasons, which was likely associated with corn residues burning. Compared to warm seasons, the MAE365, WSOC showed a positive relationship with relative contribution of fossil sources and with higher values during cold seasons, indicating the fossil derived WSOC had higher light absorption capacity and enhance the overall color of WSOC during cold seasons. To constraining the regional climate and health impact of WSOC, this study suggests that mitigation strategy should consider the spatiotemporal variations in the sources, formation pathways and light absorption properties of WSOC.