Being complex and special, C⁴ISR requirements are, often comprehended and expressed in various ways. Nowadays the results of C⁴ISR requirements development are unsatisfactory. Therefore, the authors put forward a new approach: modeling C⁴ISR requirements based on ontology. In this paper, the ontology of the basic categories and relationships needed to represent C⁴ISR requirements is present. Ontology model and semantic ontology model are included. In particular, the research focuses on clarifying the domain knowledge about C⁴ISR requirements. After that, a procedure for modeling C⁴ISR requirements based on ontology is supplied. Finally, an illustration is provided to show the feasibility,and effectiveness of the approach, indicating its promising prospect.