Abstract: Complexity of nuclear reactor experiment systems always is one of important factors which limit  the experimental technology development and innovation. Digital experiment of nuclear reactor engineering is introduced to improve the ability to deal with the complexity of experiment systems. The objective of digital experiment is to establish a unified and efficient work environment throughout the whole life cycle of the experiment programs of nuclear reactors. The high-level system architecture of digital experiment is constructed based on the method of system engineering in this paper. It consists of business architecture which is constituted by V model and business scenario diagram, experimental infrastructure architecture which is constituted by logic diagram of intellectualization, and layered architecture of digital experiment platform which is constituted by business administration system in the business layer, experimental design simulation environment system in the application layer, experiment knowledge system in the knowledge layer and basic data administration system in the resource layer. The application example for PRS experiment validates the effectiveness of the above system architecture of digital experiment as the whole logic framework of the digital experiment platform.