The　joint　has　a　significant　effect　on　the　dynamic　characteristic　of　the　mechanism,　and　the　identification　of　the　stiffness　of　the　joints　has　become　a　key　problem.　In　this　paper,　a　method　is　presented　for　identifying　the　dynamic　characteristic　of　joints.　An　experiment　is　designed　to　test　the　dynamic　parameter　of　the　bolted　joints　specimen;　the　identification　method,　based　on　experiment,　has　a　high　accuracy　result.　By　taking　a　specimen　to　experiment　and　identify　the　dynamic　characteristic　of　joints,　the　relationship　between　the　preload　on　the　bolts　and　the　joints　stiffness　is　acquired.　In　order　to　validate　the　accuracy　of　the　result,　the　FEM　software　is　used　to　simulate.　There　are　only　a　small　discrepancy　between　the　results　of　identification　and　simulation.