Abstract: In the knowledge economy era, the rapid flow channels represented by high-speed rail (HSR) and online information flow promote cross-border development between cities. This study constructed a conceptual model of cross-border development from the perspective of flow space. Taking the Yangtze River Delta Region (YRDR), China, as a case study, we apply the Speaker-listener Label Propagation Algorithm (SLPA) to detect the heterogeneity patterns of cross-border development shaped by HSR flow and information flow in 2021. Results show that cross-border development between cities is more evident under information flows compared to HSR flow. Furthermore, intra-provincial cross-border development predominates under HSR flow, whereas inter-provincial cross-border development is more frequent under in-formation flow. Additionally, information flow leads to more shared or competitive nodes in cross-border development across different communities. In the future, leveraging these nodes’ intermediary role will be key to driving the next phase of regional integration. This research will enhance and broaden the theoretical frameworks for cross-border integrated development, flow space, and regional coordinated development.