Abstract: As an accelerator and stabilizer of economy growth in China, the digital economy plays a crucial role in realizing the "dual-carbon" policy objectives.Based the balanced panel data from 26 cities in the Yangtze River Delta from 2011 to 2019, this paper measures the level of digital economy development employing entropy weight method and empirically analyzes the relationship between digital economy development and urban carbon emissions intensity, as well as the underlying mechanisms employing two-way fixed effects and mediation effects model.The results indicate: (1) There exists an inverted "U-shaped" relationship between digital economy development and urban carbon emissions intensity, which remains valid after a series of robustness tests; (2) Mechanism analysis reveals a "U-shaped" relationship between urban digital economy development and industrial structure upgrading, with digital economy indirectly affecting urban carbon emissions intensity through its influence on industrial structure upgrading; (3) Before and after the turning point of the inverted "U-shaped" relationship between digital economy development and urban carbon emissions intensity, green innovation capability exhibits respectively a "masking effect" and a "mediation effect"; (4) The digital economy development of the cities with lower levels of economic development in the Yangtze River Delta tend to experience higher carbon emissions compared to cities with higher economic development levels.Additionally, the role of digital economy development in promoting carbon emission reduction is more pronounced in "smart city" pilot cities compared to non-pilot cities.Finally, based on the research findings, relevant policy recommendations are proposed, which hold significant implications for achieving green and low-carbon development in the digital economy era