<p>Assessing the dual impact of urbanization on the carbon budget balance is crucial for developing low-carbon cities and achieving China's "dual carbon" goals. This study integrates the dual perspectives of carbon emissions and carbon absorption, specifically focusing on the county level as a fine-scale analytical unit. We selected 53 county-level units in Jiangsu Province from 2000 to 2020 as the research objects. By measuring their urbanization development level and carbon budget balance coefficient, we explored the impact of urbanization on the carbon balance with the help of geographically and temporally weighted regression model. The results revealed the following: (1) County-level urbanization in Jiangsu Province exhibited significant growth, with high-value areas concentrated in southern Jiangsu and some urban areas in central and northern Jiangsu. (2) The carbon deficit situation in various counties of Jiangsu Province has intensified, which is more serious in southern Jiangsu. (3) County-level urbanization negatively affected the overall carbon balance, but this effect was moderate during the study period. (4) From the perspective of different dimensions, county-level economic, population and spatial urbanization all have negative effects on the carbon balance, and the degree of impact decreases successively, whereas social urbanization has a positive role in promoting the realization of carbon neutrality. This paper argues that guiding economic development with low-carbon principles, attaching importance to ecological restoration and improving regional coordination mechanisms are the core strategies that Jiangsu Province can employ to achieve net carbon budget balance in the future.</p>