Abstract: Regional integration refers to the free flow of production factors to achieve market openness and full competition. To achieve China's 'dual carbon' strategic goal, the impact of regional integration on the ecological environment has attracted widespread attention. Diverse energy consumption preferences in various regions inevitably lead to the spatial transfer of carbon emissions and the flow of production materials. Therefore, the relationship between regional integration and carbon emission transfer should be critically examined to achieve high-quality green development. This study used 41 cities in the Yangtze River Delta as empirical objects and selected 2011, 2014, 2017 and 2020 as the time nodes. The regional integration network was built based on five dimensions: transportation, market, industry, information and culture. Night light data were used to estimate urban carbon emissions. The carbon emission transfer network between cities was simulated using the multi-regional input-output table. From the perspective of network form, structural correlation and interaction, we used social network analysis, cumulative distribution function, bivariate local spatial autocorrelation, ordinary least squares (OLS) and random forest regression model to quantitatively analyse the intensity, direction, trend and geographical difference of regional integration and its impact on carbon emission transfer. We found that the Yangtze River Delta had a heterogeneous spatial organisation pattern of regional integration and carbon emission transfer networks; however, the network topology had a significant correlation. The Yangtze River Delta's regional integration had a positive effect on carbon emission transfer and also showed distinct stage characteristics, implying that building integration would accelerate the flow of carbon emissions in the current stage. However, with the continuous optimisation of economic geography patterns and resource allocation, the positive relationship between regional integration and carbon emission transfer was likely to change. Influenced by the level of development, coordination mechanism, and spatial proximity, the spatial optimisation effect of integration construction within the Yangtze River Delta was better than that between its sub-regions. However, administrative barriers continued to hinder the low-carbon and the coordinated development of the Yangtze River Delta.