Abstract: Carbon sequestration service can directly fix CO₂ in the atmosphere through the photosynthesis of natural vegetation, and the balance of supply and demand is crucial for mitigating the trend of global warming. However, most of the current studies focused on the supply of carbon sequestration service, and few focused on regional carbon supply-demand balance. The Yangtze River Delta Ecological Greening Development Demonstration Area (Demonstration Area) is the first step and breakthrough to implement the integration development strategy in the Yangtze River Delta. It is also the key area to achieve the carbon peaking and carbon neutrality goals in the Yangtze River Delta.Taking the Demonstration Area as a study area, this paper evaluated the supply of carbon sequestration service based on CASA model, and identified the demand of carbon sequestration service based on population density method. This paper also explored the supply, demand and supply-demand ratio of carbon sequestration service.The results showed that, in terms of supply, the spatial distribution of carbon sequestration service in different towns was relatively balanced from 2000 to 2020. The total carbon sequestration increased from 1.10×109 kg to 1.24×109 kg, with a fluctuating trend. In terms of demand, the demand for carbon sequestration service increased from 7.15×109 kg to 4.16×1010 kg from 2000 to 2020, an increase of nearly five times. The demand for carbon sequestration service in all towns showed an increasing trend. From 2000 to 2020, the carbon sequestration supply was difficult to meet its demand, and the supply-demand ratio continued to decline, indicating a tense relationship between supply and demand. Finally, based on the supply, demand and supply-demand ratio of carbon sequestration services, this study carried out carbon sequestration service zoning. This paper aimed to put forward targeted decision-making suggestions for the realization of carbon peaking and carbon neutrality goals in the Demonstration Area.