To　present　structural　vulnerability　analysis　close　to　real-world　failure　situations,　a　practical　method　considering　material　plastic　properties　was　developed　for　calculating　the　component　importance　coefficients　of　a　truss　structure.　The　structural　design　was　then　further　optimized.　Firstly　elastic-plastic　material　properties　were　assigned　for　all　the　structural　components,　whose　plastic　situations　and　failure　patterns　were　defined　by　their　stiffness　loss.　During　the　plastic　period,　the　truss　bearing　capacity　was　considered　by　means　of　additional　loads.　Secondly,　the　relationship　between　structural　stiffness　and　deformation　matrices　was　established　to　find　the　inherent　connection　between　components＇　displacements　and　deformations.　After　that,　the　plastic　importance　coefficient　of　each　component　could　be　deduced.　Lastly,　through　predefining　the　worst　load　scenario　and　the　failure　pattern,　the　component　design　of　the　truss　structure　was　optimized　using　the　developed　method.　The　analysis　results　demonstrate　that　the　material　plastic　properties　affect　the　evaluation　of　importance　coefficients.　The　truss　failure　patterns　become　more　rational.　Meanwhile,　after　design　optimization　the　components　better　utilize　their　resistance　under　external　loads.　©　2018,　The　Editorial　Board　of　Journal　of　Basic　Science　and　Engineering.　All　right　reserved.