Abstract: In the context of dual carbon goals, the synchronous resonance between carbon emission efficiency (CEE) and high-quality economic development (HQED) has emerged as a crucial driver for low-carbon development in urban agglomerations. This study focused on 26 prefecture-level cities in the Yangtze River Delta (YRD) urban agglomeration in China. By employing models such as entropy weight method, Super-SBM, and geographic detector, we investigated the spatiotemporal evolution and driving mechanisms of the coupling coordination between CEE and HQED in the YRD urban agglomeration. The study revealed that: (1) CEE, HQED, and comprehensive scores exhibited significant spatial orientations, showing an "east high, west low" pattern in the east-west direction, and a "U-shaped" curve in the north-south direction, with the exception of CEE. (2) The overall development pattern of the YRD urban agglomeration showed a high-value regional development model radiating from core cities with high economic development levels such as Shanghai and Suzhou, with Shanghai exhibiting the highest degree of coupling coordination. Underdeveloped coordination levels in cities and low-value agglomeration areas exhibited a phenomenon of regional lock-in, presenting a spatial agglomeration pattern of "the weak remain weak". (3) Various driving factors might promote the coordinated development of cities at different time periods and to varying degrees. Among them, the single-factor driving forces of economic foundation and technological innovation were found to be prominent, while environmental regulations, human capital, and industrial structure factors with lower single-factor influence exhibited significantly increased driving forces when interacting with other factors. In light of this, policy recommendations for promoting the coordinated development of urban agglomerations were proposed in this study, which included optimizing urban layout forms, providing targeted assistance to low-value lock-in areas, and fully leveraging internal and external driving forces for coordinated development.