With the mature of the national defense field,the importance of requirement generation is rapidly increasing.By demonstrating the top-level requirements,the effective traction for future development is achieved.As national defense acquisition is a typical complex system,which involves many processes and participates,it is necessary to propose an effective method based on system engineering theory,in order to guide the acquisition process and lead to a successful result.For implementing the requirement generation,the Joint Capability Integration and Development System (JCIDS) has been constructed.By defining a set of unambiguous and executable steps,the framework of requirement generation has been clarified,which transfers the defense acquisition from “threat-based” model to the “capability-based” model.Therefore,elaborating the requirement generation mechanism in defense acquisition is focused,especially for its compositions and operation process,in order to comprehend essentials of the defense acquisition and provide a reference for the related work.