Many information retrieval(IR) systems retrieve relevant documents based on exact matching of keywords between a query and documents. This method degrades precision rate. In order to solve the problem, we collected semantically related words and assigned semantic relationships used in general thesaurus and a special relationship called keyfact term(FT) manually. In addition to the semantic knowledge, we automatically constructed statistic knowledge based on the concept of mutual information. Keyfact is an extended concept of keyword represented by noun and compound noun. Keyfact can be a verb and an adjective including subject or object term. We first retrieved relevant documents with original query using if * idf weighting formula and then an expanded query including key facts is used in both second document ranking and word sense disambiguating. So we made an improvement in precision rate using keyfact network.