It is a task of travail to build knowledge model. The main problems of knowledge modeling are how to share and reuse repository better, and how to implement semantic reasoning and query. Ontology is an efficient way of knowledge-modeling. In this paper with automatic control theory, the application in constructing teaching-domain knowledge model based on ontology is illustrated, and net interactive XML is used highly to describe the ontology. 7-tuple is used to describe the conception of teaching-domain, and the meaning and formal-foundation definition of every tuple is described in details. Therefore, the teaching-domain knowledge ontology will be an integrated, complexity and clear semantic web structure model.