<p>Realizing the synergistic effect of urban carbon-reduction and water-saving (CRWS) is of great significance for improving the urban carbon-water nexus and promoting urban sustainable development. From the perspective of the synergistic impact of intensive water resource utilization on carbon emissions, a theoretical framework is constructed. The relevant data on water resources and carbon emissions of the Yangtze River Delta Urban Agglomeration (YRDUA) from 2014 to 2023 are taken as the research objects for analysis. And a series of fixed effect models are adopted to evaluate the synergistic and regulatory effects of urban CRWS. Results show that the production water supply intensity has a positive impact on carbon emission intensity, while production water-saving intensity and ecological water intensity have negative impacts on carbon emission intensity in the YRDUA. Technical factors negatively regulate the synergy of carbon emission intensity and production water supply intensity. Structural factors negatively regulate the synergy between carbon emission intensity and water resource intensive utilization intensity. Technology, structure and scale factors have more significant effects on the synergistic effect of CRWS in areas with higher urban development level.</p>