Under the influence of coastal perimeter, the physical and chemical environment of coastal wetland soil changes dramatically, which affects the SOC content and carbon sequestration function of wetland ecosystem. In order to reveal the influence of coastal perimeter and its history on the carbon sink function of coastal wetlands, this study focuses on the eastern coastal zone of Chongming Island in Shanghai. It compares changes in soil physical and chemical environment, organic carbon content, and active components such as Dissolved Organic Carbon (DOC), Microbial Biomass Organic Carbon (MBC), and Easily Oxidized Organic Carbon (EOC) in coastal wetlands affected by reclamation history of <10 years, 10—20 years, 20—30 years, and >30 years. The study also examines the allocation ratio and correlation of active organic carbon to analyze the impact of coastal enclosure and enclosure history on changes in SOC and its active components in coastal zone wetlands. Recommendations for the protection and management of coastal zone wetlands based on land-sea coordination are proposed. The results showed that: (1) After coastal reclamation, the soil physical and chemical environment of wetlands significantly changed (P<0.05), with decreases in soil Electrical Conductivity (EC), Total Nitrogen (TN) content, and clay. EC decreased gradually with the increase in reclamation years, while TN content and clay showed a trend of initially decreasing and then increasing with reclamation age. (2) SOC and DOC contents decreased after coastal reclamation, with a pattern of first decreasing and then increasing with reclamation years. MBC and EOC exhibited a trend of initial increase, subsequent decrease, and then increase after 30 years of reclamation. (3) The ratios MBC/SOC, DOC/SOC, and EOC/SOC in the coastal zone were significantly higher than those in the inland wetland (P<0.05), showing an initial increase and subsequent decrease with reclamation years, suggesting that SOC stability decreased initially after reclamation and then increased with time. (4) There was also a positive correlation (P<0.05) between SOC, DOC, MBC, and EOC, and significant correlations between organic carbon components and soil physicochemical characteristics. The findings contribute to understanding the impact of coastal enclosures on the carbon sequestration capacity of coastal ecosystems and provide a scientific basis for enhancing carbon sequestration and the function of coastal wetlands under integrated land and sea planning. The study also offers insights for the protection and management of China"s "double carbon" goal