Now　the　ontology　construction　is　mainly　based　on　manual　mode,　the　whole　process　requires　a　lot　of　manpower　and　material　resources.　In　this　paper　we　proposed　a　semi-automatic　domain　ontology　construction　framework　based　on　web　crawler.　The　framework　can　fetch　domain　data　on　network　and　extract　semantic　knowledge　through　language　methodology　and　statistical　methods.　Finally,　we　construct　ontology　using　the　domain　ontology　modeling　method　based　on　extensions.　The　framework　can　save　the　investment　of　manpower　and　human　resources　in　the　manual　construction　mode.