Abstract： The high sequestration efficiency and strong sequestration potential of land-sea interaction regions are important nature-based, long-term solutions to climate change and the achievement of “carbon peaking” and “carbon neutrality”. In order to reveal the sources and forms of dissolved organic matter (DOM) in the land-sea interaction stratigraphy along the south coast of Laizhou Bay, and to enrich the understanding of carbon sources and sinks in the land-sea interaction region, the interstitial water from drill core was collected from November to December 2021 and analyzed for UV-visible absorption spectra and three-dimensional fluorescence spectral signatures of chromophoric dissolved organic matter (CDOM). The analyses showed that dissolved organic carbon and a(320) are both characterized by large and high concentrations after the second transgression. The difference in dissolved organic matter composition and properties of terrestrial-phase interstitial water is greater than that of marine-phase interstitial water. Of the five fluorescence components identified by parallel factor analysis and matched by OpenFlour, the humus-like components contributed 77% of the total fluorescence intensity, except for the bottom stratum. The fluorescence index and biogenic index show that the core interstitial water chromophoric dissolved organic matter is dominated by the contribution of microbial reproduction activities, and the longer the burial, the more significant the microbial contribution, and there is no significant difference between the terrestrial and marine phases. The results of principal component analysis show that the compositions have some differences in different sedimentary stages, but the composition and properties of the interstitial water dissolved organic matter gradually converge as the sedimentary process occurs. The humus is highly matured in long time scales.