Technology　about　ontology　plays　an　important　role　in　all　kinds　of　technologies　about　the　Semantic　Web.　OWL,　the　standard　web　ontology　language　is　proposed　by　W3C.　Vocabularies　in　OWL　only　represent　certain　and　complete　concepts　and　roles.　In　order　to　represent　fuzzy　knowledge,　this　paper　extends　existing　OWL　language　by　encoding　fuzzy　constructors,　axioms　and　constraints　and　maps　semantics　of　these　new　vocabularies　to　fuzzy　description　logic.　Extended　OWL　can　represent　fuzzy　ontology　and　resolve　some　fuzzy　entailment　tasks　by　constraint　propagation　calculus　of　fuzzy　description　logic.　©　2005　IEEE.