In　the　economic　environment　of　the　world　at　present,　the　competition　among　the　enterprises　is　the　competition　of　the　knowledge　right.　Because　the　patent　is　the　most　concentrated　carrier　of　the　knowledge,　the　efficiency　of　patent　retrieval　and　utilization　is　an　important　way　of　the　enterprises　to　understand　their　competitors,　track　the　developed　trend　of　the　industrial　technique　and　improve　the　independent　innovation　capability　and　core　competitiveness　of　their　own.　But　at　present　patent　information　retrieval　systems　based　on　the　keyword　match　can＇t　satisfy　the　users＇　demands　on　accuracy　and　completeness.　So,　this　paper　proposes　to　establish　patent　domain　ontology,　and　expand　the　query　based　on　it　to　realize　semantic　retrieval　and　improve　the　comprehensiveness　and　accuracy　of　the　patent　information　retrieval.　©　2010　IEEE.