Oceanic dissolved organic matter(DOM) is important for global biogeochemical cycles and also plays important roles in the response of ecosystems to climate change. However,isolation and characterization of DOM from seawaters is still not readily achieved due to the complexity of DOM in its composition and structure as well as high salinity of seawaters. China is a country with the biggest mariculture yield. However,the isolation and characterization of DOM in mariculture seawaters is far less well studied. In this study,we employed coupled electrodialysis /reverse osmosis(ED/RO) to isolate DOM from mariculture seawaters. Results indicate the recovery of dissolved organic carbon(DOC) was 66. 8%. Scaled UV-Vis absorption spectra,spectral slopes,and the molar C ∶ N ratio indicate that the isolated samples represent DOM in the source mariculture seawaters. This study is helpful to unveil the cycling and transformation of DOM in the coastal seawaters of China.