For sake of doing research on requirements-level software automation and developing an object-oriented requirements analysis support system, the authors have proposed a hierarchical object-oriented requirements model NDHORM(Nanjing daxue hierarchical object-oriented requirements modelling), which includes an object relationship model, a class relationship model and a class dictionary. First, the authors discusse object-oriented requirements analysis methods, then introduce the components, hierarchical structure of NDHORM, and its object refinement mechanism at length in this paper. Further, the authors chiefly address the modeling process of NDHORM. Finally, its mechanical support system is also reported.