<p>As economic growth increasingly conflicts with environmental protection, green technology innovation (GTI) has become essential for sustainable development. This study applies complex network theory and social network analysis to examine intra- and inter-cluster collaboration networks in the Yangtze River Delta (YRD) based on green patent data. Results reveal distinct spatial disparities in green patent collaborations, following a pattern of "strong in the east and weak in the west". Enterprises play a leading role in both intra- and inter-cluster networks, although their level of participation shows opposite trends. Key technologies in both networks are dominated by power-related collaborations. However, over time, intra-cluster collaborations have increasingly focused on new energy vehicles. Additionally, Hefei's role in intra-cluster collaboration has steadily grown, while Beijing has emerged as the most influential city in inter-cluster collaboration. Both networks exhibit a significant core-periphery structure. Although YRD cities predominantly engage in inter-cluster collaboration, they are gradually shifting toward intra-cluster partnerships. Therefore, government efforts should prioritize GTI investment, collaborative platform development, and tailored policies for specific collaboration types.</p>