Abstract: The transmission of civil aviation passenger information among different countries with the entry and exit of international flights is a typical situation 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 specifies the requirements for cross-border data reporting. It introduces the principles of “requirements for three properties” “personal rights and freedoms” and “necessary and proportionate” to facilitate the formulation of guiding documents for advance passenger information (API) and passenger name record (PNR), and to fulfil the multiple functions of passenger data in enhancing the convenience and security of transportation. A prominent problem in cross-border flow of civil aviation passenger data is that there are significant differences in legislation, regulation, and technical standards between countries, which hinder the effective flow of data. In this regard, ICAO still needs to continuously play the role of communication and coordination, and integrates 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 system and regulatory system to ensure the orderly cross-border flow of civil aviation passenger data.