Voronoi　diagram　is　an　important　branch　of　computational　geometry,　which　plays　a　significant　role　in　both　computational　geometry　theory　and　application.　Voronoi　diagram　has　been　widely　applied　in　many　fields,　especially　in　the　field　of　geography　spatial　facilities　location.　In　this　paper,　Voronoi　diagram　was　applied　in　power　system　substation　optimization　planning,and　it　advanced　an　improved　orientation　strategy,　namely　the　most　greatly　convex　polygon　electrical　load　orientation　strategy　which　is　used　in　the　power　system　substation　optimization　location.　The　method　of　this　paper　could　effectively　combine　the　computational　geometry　and　the　power　system　substation　optimization　planning.　The　efficiency　and　applicability　of　this　method　have　been　proved　by　the　case　study　of　220kV　substations　optimization　planning　in　a　city.　©　2010　IEEE.