Domain analysis is the activity of identifying and representing the relevant information in a domain, so that the information can be shared and reused in similar systems. But until now, no efficient approaches are available for capturing and representing the results of domain analysis and then for sharing and reusing the domain knowledge. This paper proposes an ontology-oriented approach for formalizing the domain models. The architecture for the multiple-layer structure of the domain knowledge base is also discussed. And finally, some genetic algorithm-based methods have been given for supporting the knowledge sharing and reusing.