Node　localization　plays　a　critical　role　in　wireless　sensor　network.　This　paper　emphatically　analysised　the　signal　strength　based　on　ranging　method(RSSI)　of　wireless　location　technology　and　the　theory　of　three-point　positioning　method.　On　that　basis,　extended　it　and　proposed　a　theoretical　values　combine　experience　values　databaces　based　on　the　three-point　positioning　method.　This　positioning　algorithm　has　a　less　relative　errors　by　using　different　databases(experience　value　database　and　anchor　node　initial　position　distance　database)according　to　different　conditions.　Finally,　we　verified　the　proposed　method　through　MATLAB　simulation.　The　results　show　that　this　positioning　algorithm　is　effective.　It　can　effectively　solve　the　problem　which　may　caused　by　environmental　effect　and　the　heavy　actual　measurement　workload.　What＇s　more,　it　also　can　reduce　the　difficulties　and　workload　of　locating　the　random　dropped　wireless　sensor　network　nodes.　©　Springer-Verlag　Berlin　Heidelberg　2011.