Abstract: With the development of military information systems, acquiring knowledge from operational data becomes a signi¯cant issue in C2 area. In the ¯rst place, this paper argue that knowledge acquisition is necessarily required for military information systems to be interoperable and intellectual. And the tasks of acquiring knowledge from operational are were presented. Then based on ontology, the constructing approaches of operational knowledge are delivered. And thoroughly, the methods of acquiring operational ontology based-on operational data are discussed, including the means for forming schema ontology, extracting instance ontology and ontology matching. In the end, some issues about inference and extension of operational knowledge are addressed.