To　find　the　weak　link　of　the　structural　stiffness　is　important　to　improve　machine　tool　stiffness.　However,　how　to　overcome　the　static　deformation　with　difficulty　acquisition　is　a　difficult　problem　in　machine　tool　structure.　The　article　takes　the　cantilever　beam　structure　as　a　numerical　example,　the　weak　link　is　modeled　as　EA　reduction　in　stiffness.　Thorough　finite　element　simulations　are　performed　to　assess　the　robustness　and　limitations　of　the　method　in　several　scenarios　with　single　and　multiple　weaknesses.　The　sensors　are　used　to　acquire　the　acceleration　data,　the　structural　modal　parameters　are　obtained　by　the　singular　value　decomposition　technique,　and　the　dynamic　characteristics　are　systematically　reconstructed　by　using　the　modal　state-space　method　to　obtain　static　stiffness.　Then,　an　identification　method　proposed　by　measured　data　and　reconstructed　data　to　identify　the　weak　link　of　stiffness　of　the　cantilever　structure.　Furthermore,　the　comparison　of　numerical　and　experimental　results　validate　the　correctness　and　effectiveness　of　this　method.　The　research　has　certain　practical　engineering　value　and　provides　an　accurate　guidance　for　the　optimization　of　machine　tool　stiffness.