Abstract: Currently, the driving effects of key influencing factors and their dominant roles in carbon sequestration of terrestrial ecosystems in rapidly urbanizing areas have not yet been accurately quantified and identified. This limitation constrains the in-depth scientific understanding of urban ecosystems and affects the scientific formulation and effective implementation of ecological protection measures such as new urbanization and urban renewal. Based on the analysis of spatiotemporal characteristics of vegetation carbon sequestration at the county scale in the Yangtze River Delta from 2001 to 2020, this study investigated the dominant factors and driving contributions of 12 indicators related to human activities, climate change, elevated CO₂ concentration, and nitrogen deposition to the changes in vegetation carbon sequestration by using first-order partial derivative attribution analysis. The results show that: (1) the vegetation carbon sequestration in the Yangtze River Delta showed a slight increasing trend, with significant increases in the northwestern plain counties and decreases in the southeastern counties from 2001 to 2020. (2) Human activities, climate change, and nitrogen deposition positively drove the carbon sequestration (CS) of terrestrial vegetation in 118, 182, and 197 counties in the Yangtze River Delta, respectively, while CO₂ concentration had a significant inhibitory effect on CS in 190 counties. Meanwhile, there was significant spatial heterogeneity in driving contribution of 12 indicators to the vegetation carbon sequestrationt. (3) Human activities, climate change, elevated CO₂ concentration, and nitrogen deposition were the dominant factors for the changes in vegetation carbon sequestration in 124, 70, 3, and 5 counties, respectively. Recommendations are as follows: (1) systematically enhance the functional and carbon sink service capacity of urban landscapes by improving the biodiversity of different green spaces and integrating fragmented urban green patches. (2) Further explore carbon sequestration potential of mountainous counties through measures such as soil nitrogen and phosphorus improvement considering the high background value of vegetation carbon sinks. (3) Strengthen the construction of urban ecological infrastructure during urban renewal, and develop differentiated policy measures based on Natural based Solutions (NbS) and the dominant factors of vegetation carbon sequestration to enhance the urban climate adaptation capacity.