A　space　structure　or　one　part　of　it　could　be　abstracted　into　a　directed　graph　by　graph　theory,　especially　for　wavelet　intelligent　methods.　Distance　matrix　is　determined　according　to　the　connective　relationship　of　each　element,　and　a　new　optimal　sensor　placement　method　is　put　forward　by　applying　Floyd-Warshal　algorithm　and　considering　structural　modal　parameters,　such　as　modal　kinetic　energy　and　modal　strain　energy.　Optimal　placement　of　sensors　is　carried　out　to　a　single-layer　bielliptical　reticulated　shell　by　the　method　in　this　paper.　The　feature　vectors　of　the　signals　from　acceleration　sensors　located　on　the　space　structural　nodes　under　ambient　random　excitation　are　extracted　by　numerical　simulation.　Structural　damage　states　are　detected　by　support　vector　machine.　The　optimal　sensor　placement　method　and　wavelet　intelligent　method　are　proved　to　be　effective　and　accurate　by　analyzing　and　comparing　the　results.　©　2006　Taylor　&　Francis　Group.