Abstract: Investigating the spatial differentiation of carbon balance at the urban cluster scale can provide scientific basis for the coordinated and sustainable development of urban cluster regions; Utilizing 42 cities within the Chengdu-Chongqing urban agglomeration as the research area, this study examined the economic contribution coefficients and ecological support coefficients of carbon balance for each city for 2005, 2010, 2015, and 2020. Furthermore, carbon balance zoning was conducted by employing the second-order clustering method; The regional ecological carbon balance exhibited an initial decline followed by an increase, displaying a spatial pattern of lower values in central areas and higher values in peripheral regions. On the other hand, the economic carbon balance followed a similar pattern of decreasing and then increasing, with the spatial characteristics of higher values in the western areas and lower values in the eastern areas. Based on the outcomes of clustering analysis, the 42 cities were categorized into four zones: carbon source optimization area, carbon sink optimization area, carbon balance economic compensation area, and carbon balance ecological compensation area. This classification formed the foundation for suggesting diverse optimization measures for carbon balance within these zones; The carbon balance within the Chengdu-Chongqing urban agglomeration exhibited distinct spatial differentiation features, compounded by existing ecological and economic barriers between Chengdu and Chongqing cities.