Cross border data flow is a critical issue in the digital economy era and a focal point of strategic competition among major powers. This paper proposes a three-dimensional analytical framework integrating "network architecture-nodal influence- policy dynamics." Based on the international bandwidth data of the Tele Geography database, this paper uses complex network analysis methods to construct the global cross-border data flow network in 2018 and 2022, revealing the evolution characteristics of its topological structure and the changes in the control power of key node countries. The results show that the scale of global cross-border data flow continues to expand, the network connection is becoming increasingly close, and the trend of multipolarization is significant, but the dominance is still concentrated in developed countries such as the United States and Germany; China's status continues to rise. Five typical economies are further selected to analyze the differences in their policy positions: 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. This research provides an empirical foundation for comprehending the evolution of cross-border data flows and informs policy formulation for China's digital governance strategies.