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