Abstract: The land-sea interaction and its mechanism in the Pearl River estuary are complex. Identifying the land-sea interaction and the recording of human activities in sediments is of great significance for the protection of marine ecological environment and the understanding of coordinated coexistence between humans and nature. Total organic carbon (TOC), total nitrogen (TN) and stable carbon and nitrogen isotope (δ¹³C_org and δ¹⁵N_tot) combined with a three-endmember-mixing model were measured to analyze the characteristics and sources of organic matter in surface sediment samples of Lingdingyang bay, the Pearl River estuary. The results indicate that the main sources of organic matter in Lingdingyang bay sediments are terrestrial, marine and sewage sources, with multiple sources. The average percentage contributions for terrestrial, marine and sewage sources in surface sediments are 48.1%, 42.3% and 9.7%. It shows that the organic matter in the surface sediments of the Pearl River estuary has the characteristics of multi endmember mixing dominated by terrestrial organic matter input, while the organic matter from sewage generated by human activities accounts for a relatively high proportion, which is worth conducting further research.