Domain requirements are fundamental for software reuse and are the product of domain analysis. This paper presents an ontology based approach to elicit and analyze domain requirements. An ontology definition is given out. Problem domain is decomposed into several sub problem domains by using subjective decomposition method. The top-down refinement method is used to refine each sub problem domain into primitive requirements. Abstract stakeholders are used instead of real ones when decomposing problem domain and domain primitive requirements are represented by ontology. Not only domain commonality, variability and qualities are presented, but also reasoning logic is used to detect and handle incompleteness and inconsistency of domain requirements. In addition, a case of ?spot and futures transaction? domain is used to illustrate the approach.