Abstract. In this paper, we propose an ontology-based event description language, OntoEvent, for semantic event modeling in CEP system. In OntoEvent language, complex events are modeled and described in the form of event ontology. We propose the concept of nature language event constructor and define them by synonym set of WordNet database to describe logical and temporal event relationship in OntoEvent. We demonstrate event ontology examples in application domain of smart home, and our analysis shows that OntoEvent is of rich expressiveness compared to other related languages.