Abstract: The impact of the flood event on the distribution and source of particulate organic carbon(POC) in Changjiang (Yangtze River) Estuary and adjacent waters was analyzed based on the data of temperature, salinity, total suspended matter(TSM), POC and δ13CPOC ,which were collected during the July 2020 flood. The results show that POC is negatively correlated with salinity (r2=0.41, p＜0.01), and positively correlated with TSM (r2 =0.92, p＜0.01). The mixing of salt and fresh water is an important factor affecting the distribution of POC. The distribution of δ13CPOC values in the surface water indicates that the phytoplankton production is another important factor affecting the distribution of POC in the northeastern part of the study area. Flood events reduce the concentration of terrigenous POC due to the dilution of high runoff, meanwhile, light δ13CPOC values in the southeastern part of the study area indicate that flood events could expand the influence range of terrigenous POC in the East China Sea.