To solve the problem that Non-functional property specification & verification in web service (WS) flow has become indispensable,an ontology-based approach was presented for specifying and verifying time constraints consistency in WS flow. Time OWL-S was built to express basic time information of WS flow roundly. Meanwhile, Petri Nets Ontology was enriched with time semantic information, which can describe WS semantics based on OWL. The mapping definition between Time OWL-S and extended Petri Nets Ontology was also given. Through extending OWL-S API，annotated OWL-S model was transformed into PNML, a standard format to describe Petri Nets Ontology. A verification system was taken to illustrate the correctness and feasibility of the verification process.
