Abstract: In order to improve the security and the margin of safety of nuclear power plant, the research on requirement analysis of digital reactor protection system for advanced pressurized water reactor nuclear power plant was developed. Based on the known technology, a requirement analysis report was performed. A kind of three-levels pyramidal hierarchy was adopted in the requirement analysis, and the design characteristics of the requirement analysis were described in the analysis report. This hiberarchy can directly illuminate the design characters and logical achievement of the requirement analysis for advanced pressurized water reactor digital protection system.