the air traffic management (ATM) system is a comprehensive information-based intelligent system that provides seamless services and dynamic integrated management of air traffic and airspace through the cooperation of all relevant parties in civil aviation. The ATM adopts an integrated "space-air-ground" network structure to provide reliable services for the security and efficiency of civil aviation flights, which is an important infrastructure to support and guarantee civil aviation transportation and an important support point for the development of civil aviation as a whole. The composition of the ATM is wide and complex, and contains many business systems and user types. In the face of the increasingly serious information security threats, the business collaboration of ATM and the shared use of ATM data are subject to certain restrictions and challenges. According to the Aviation Network Security Strategy released by International Civil Aviation Organization (ICAO) in 2019, there is an urgent need to research the basic theories, core methods and key technologies for ATM information security assurance that are compatible with the characteristics of ATM composition and information security assurance needs. From the core research objective of ATM information security assurance, this paper designs a future ATM security architecture based on blockchain technology, referred to as ATMChain, to meet the real operational needs of ATM trustworthiness, security and availability. ATMChain takes ATM trustworthy services as the core and builds an ATM information security base with "endogenous security" features. Then, three security function modules, namely, trusted authentication, data sharing, and access control, are designed to realize the 4A (Authentication, Account, Audit, Authorization) security functions of ATM. Finally, this paper provides a comprehensive analysis and performance evaluation of ATMChain security architecture. The results show that the research in this paper will help solve the current bottlenecks in ATM information security assurance, promote technological innovation, and ultimately facilitate the realization of the vision of global ATM interoperability proposed by ICAO.