In　practical　engineering,　bolt　connection　structures　are　widely　used　because　of　their　advantages　of　simplicity,　reliability　and　easy　disassembly.　The　stiffness　of　bolted　connection　is　between　hinge　and　rigid　connection,　but　it　is　usually　treated　as　hinge　or　rigid　connection　directly　in　engineering.　In　order　to　improve　the　accuracy　of　numerical　simulation　of　bolted　connection　structures　and　truly　reflect　the　dynamic　characteristics　of　bolted　connection　structures,　it　is　necessary　to　determine　the　true　stiffness　of　bolted　connection　according　to　the　experimental　data.　The　six　degree　of　freedom　spring　is　used　to　simulate　the　bolt　connection　to　establish　the　simulation　model　of　a　bolt　connection　structure.　The　spring　connection　stiffness　is　taken　as　the　design　variable,　the　residual　between　the　numerical　simulation　result　and　the　experimental　test　result　of　the　eigenvector　is　taken　as　the　objective,　and　the　residual　of　the　natural　frequency　between　numerical　simulation　result　and　the　experimental　test　result　is　taken　as　the　constraint　to　establish　the　optimization　model.　Solving　the　optimization　model　to　get　the　spring　stiffness　is　to　make　the　numerical　simulation　results　match　the　experimental　test　results　of　the　bolt　connection　stiffness.　The　static　and　dynamic　analysis　of　the　modified　bolt　connection　structure　is　carried　out,　and　the　numerical　simulation　error　of　the　bolt　connection　structure　is　analyzed.　Numerical　examples　show　that　the　real　stiffness　of　bolted　connection　can　be　determined　by　the　model　modification　method,　which　can　improve　the　numerical　simulation　accuracy　of　bolted　connection　structures,　and　provide　theoretical　basis　and　engineering　experience　for　the　precise　modeling　of　bolted　connection　structures.　©　2021,　Editorial　Department　of　CJAM.　All　right　reserved.