Cross border data flow represents a critical issue in the digital economy era and a focal point of strategic competition among major powers. A three-dimensional analytical framework integrating "network architecture-nodal influence-policy dynamics" was proposed. Based on international bandwidth data of the TeleGeography database, complex network analysis methods were applied to construct global cross-border data flow networks for 2018 and 2022, revealing the evolutionary characteristics of their topological structures and changes in the control power of key node countries. The findings indicate that the scale of global cross-border data flows continues to expand, the network connection is becoming increasingly close, and the trend of multipolarization is significant. But dominance remains concentrated in developed countries such as the United States and Germany. China's standing continues to elevate. Five typical economies are further selected to explore differences in their policy stances: the United States shifts from free flow to "conditional" regulation, the European Union strengthens data protection standards, China balances security and openness, Singapore promotes international cooperation, and Russia focuses on data localization. Empirical evidence is provided for understanding the evolution of cross-border data flows, and insights are offered for policy formulation regarding China's digital governance strategies.