Traditional keyword-based search engine does not consider the additional information provided by the structure of XML documents

it returns imprecise results often;searching according to keywords and structure information of XML documents inputted is not suitable for common users.Semantic search for XML data based on tag—keywords overcomes the limitations above

but its efficiency needs to be improved.This paper analyzes semantic information provided by the structure of XML documents deeply.It puts forward a new index structure for XML data and semantic related decision function between two nodes.Based on this

it proposes a fast semantic search algorithm for XML data.The search algorithm reduces the times to decide semantic correlation greatly.The experimental results with real data sets illustrate the effectiveness of the proposed algorithm.