Based on the analysis of particulate organic carbon (POC) and particulate nitrogen (PN) of the 155 samples collected from the 41 stations in the Bohai Bay and its adjacent sea, during the summer period in 2006, combining with the data of environmental hydrology, the spatial distributions, influential factors and source of POC and PN were discussed. The results show that the concentrations of POC and PN range from 155.9 microg/L to 1363.1 microg/L, 26.2 microg/L to 225.5 microg/L, with average values of 429.5 microg/L and 111.5 microg/L, respectively. The spatial distribution patterns of POC and PN are similar in the study area. The concentrations of POC and PN in the coastal areas are higher than those in the outer shelf, and the concentrations of POC and PN are higher at the bottom water layers than those at the surface water layers. Biological effect, thermocline and concentration of TSM are the main factors affecting the spatial distribution of POC. There exists a positive correlation between POC and TSM, indicating that the source of TSM is an important factor for the POC. The POC/PN ratio varies from 3.4 to 7.0, but this result is influenced by the presence of particulate inorganic nitrogen (PIN). According to the univariate linear regression model between POC and PN, the concentrations of PIN in the samples were evaluated. Removing the content of PIN in the samples, the POC/PON ratio ranges from 5.5 to 19.8 (PON= PN - PIN), suggesting that the terrestrial input originating from the nearby rivers is also an important source of POC, in addition to the major contribution from the marine primary production. This method could be applied to identify the source of POC in other coastal areas of China.