The coastal zone serves as a critical interface for the sequestration and storage of organic carbon at the land-sea boundary,exhibiting significant spatiotemporal characteristics and patterns in organic carbon formation over long-term soil development scales.This study focused on analyzing the vertical distribution characteristics and temporal evolution patterns of Soil Organic Carbon (SOC) in silty-muddy coastal zones of the South Yellow Sea,spanning over millennia.Twenty soil profiles,each one-meter-deep,were collected from locations corresponding to historical coastline positions in Sheyang (north) and Dongtai (middle) within the study area.The spatiotemporal distribution characteristics of SOC mass fraction (SOCC),density (SOCD),and stock (SOCS) were analyzed,along with their correlation with soil physicochemical properties.The results indicated the following,1) Over millennia,SOCC in coastal cultivated soil profiles ranged from 1.00 g·kg^-1 to 24.44 g·kg^-1,and SOCD varied between 0.13 g·m^-2 and 2.78 g·m^-2,both decreasing with depth in the two regions.2) The temporal accumulation functions of SOCS differed between the two regions;in Sheyang,SOCS showed a linear relationship with pedogenic age,while in Dongtai,it exhibited a logarithmic function,primarily due to variations in soil parent materials.3) Significant correlations were observed between SOC and soil physicochemical properties in coastal cultivated land;in Sheyang,higher correlations were found between SOC and bulk density as well as total salt content,while in Dongtai,higher correlations were observed with soil texture.This study provides important insights into the dynamic characteristics and long-term storage mechanisms of soil carbon pools in coastal cultivated land.