Ecological green integration is the first move and breakthrough in the implementation of the national strategy for the development of regional integration in the Yangtze River Delta. On the basis of literature review, this paper sorts out the driving mechanism of ecological green development in the process of regional integration. Based on the panel data of 41 cities in the Yangtze River Delta, the dynamic interaction relationships of the inter-city ecological green development is identified with the VAR Granger causality test method, and the spatial correlation network of urban ecological green development is analyzed using social network analysis method. The research finds that the ecological green development of cities in the Yangtze River Delta presents a complex and multi-threaded spatial correlation network structure. The development of a city is not only related to its own, but also affected by its regional and overall network. The interaction between cities has been increasing, but the overall is not close enough. The network structure has become increasingly stable, while the hierarchical spatial structure has been broken. Moreover, there are four major growth poles, and the central city is not enough to drive the development of the surrounding areas. The formation of the plate breaks the administrative boundary, the correlation transmission has obvious gradient overflow characteristics, and the urban development moves from discrete to united gradually. The main driving factors for the evolution of the ecological green development network lies in the differences among cities, in terms of economic development level, degree of opening to the outside world, government investment in sci-tech, and geographic locations. This study further points out that in the ecological and green development in the process of regional integration, each city should break through the geographical restrictions based on its role and function in the overall network, change from “beggar-thy-neighbor” to “neighborly partnership”, improve the regional cooperation and consultation system at a smaller scale, and cultivate the network thinking driven by “attribute-relationship”, which is the key to enhancing the urban ecological green development of the Yangtze River Delta.