Abstract: At present, it is increasingly difficult for the nuclear power design products to meet user expectations for there is no effective method to collect and manage the requirement information, and it is unable to perform early the requirement verification and to change the requirements in the research and development process. In view of the above problems, this paper takes the safety injection system as an example and applies the requirement modeling to the requirement analysis process. The collection of requirements is achieved through requirement use case modeling, requirement scenario modeling and requirement logic modeling. the state diagram is implemented to ensure that the top-level design proposal meets user requirements, and the timing diagrams are compared to check for the missing and inconsistent requirements. Therefore, the early validation of requirements is realized by means of requirements modeling, ensuring that the design products meet the user requirements, and at the same time providing a reference for the further application of requirements modeling in nuclear power design.