The　evaluation　of　the　weak　link　of　machine　tool　structural　stiffness　is　the　key　link　to　improve　the　machining　performance　of　the　machine　tool.　It　is　proposed　that　the　serial　structure　of　the　machine　tool　be　equivalent　to　a　cantilever　beam　structure　and　the　static　rigidity　of　the　machine　tool　be　studied　by　using　the　method　of　dynamic　test.　A　theoretical　method　for　evaluating　the　position　of　the　weak　link　of　cantilever　beam　stiffness　and　the　magnitude　of　stiffness　by　using　the　curve　angle　index　is　proposed.　This　paper　mainly　studies　the　evaluation　effect　of　indicators.　Taking　the　MATLAB　finite　element　numerical　model　of　cantilever　beam　structure　as　a　numerical　example,　the　dynamic　test　data　of　each　node　of　the　numerical　model　are　obtained　by　using　the　state　space　method.　After　Fourier　transform,　the　angle　index　is　studied　by　taking　the　amplitude　of　0　Hz.　The　weakening　of　the　elastic　modulus　of　the　element　is　used　to　simulate　the　weak　link　of　stiffness,　and　the　evaluation　effect　of　the　corner　index　is　studied　under　the　three　conditions　of　weakening　the　stiffness　of　a　single　element,　weakening　the　stiffness　of　two　elements,　weakening　the　stiffness　of　three　elements　and　involving　noise.　The　results　of　simulation　and　experiment　show　that　the　curve　angle　can　be　used　to　better　evaluate　the　weak　link　of　the　cantilever　beam,　which　has　a　certain　practical　value　in　engineering.　©　Published　under　licence　by　IOP　Publishing　Ltd.