Abstract: The transmission of civil aviation passenger information along with international flights among different countries constitutes a typical scenario of cross-border data flow in civil aviation. Based on its responsibility to promote the development of international air transport, the International Civil Aviation Organization (ICAO) has formulated Annex 9, which explicitly outlines the requirements for cross-border data reporting. It introduces principles such as “full respect” and “necessary and proportionate restrictions” to facilitate the formulation of guiding documents for advance passenger information (API) and passenger name record (PNR), leveraging passenger data to enhance convenience and security in various ways. A prominent issue in the cross-border flow of civil aviation passenger data is the significant differences in national legislation, regulation, and technical standards, which hinder effective cross-border data flow. In this regard, the ICAO still needs to play a role in communication and coordination, integrating the strengths of international organizations and experts to advance the formulation and improvement of international standards and measures. As a major country in both civil aviation transport and data, China needs to continuously improve its domestic legislation, strengthen international cooperation, actively participate in international governance, and establish a robust safety assessment and regulatory system to ensure the orderly cross-border flow of civil aviation passenger data.