In　order　to　describe　the　dynamic　characteristics　of　a　compliant　mechanism,　the　dynamic　model　thereof　is　built.　Based　on　the　finite　element　method,　the　dynamic　equation　of　compliant　mechanism　is　developed　by　using　Lagrange　equation.　On　this　basis,　the　natural　frequencies　and　modes　of　the　mechanism　are　derived.　A　method　for　calculating　the　sensitivity　of　natural　frequencies　and　modes　to　the　design　variables　is　then　presented.　An　algorithm　for　calculating　the　strain　at　any　point　on　a　flexible　link　in　the　compliant　mechanism　is　derived.　Nonlinear　terms　in　the　strain　are　also　reckoned　in　the　algorithm.　The　dynamic　stress　at　any　position　on　the　flexible　link　is　solved,　and　the　maximum　stress　and　its　position　on　the　link　at　any　time　are　also　calculated.　The　numerical　simulation　of　a　compliant　four-bar　mechanism　indicates　that　the　dynamic　characteristic　analysis　of　compliant　mechanism　based　on　finite　element　is　feasible　and　effective,　and　the　analysis　on　strain　and　dynamic　stress　of　the　link　of　compliant　mechanism　has　important　significance　to　the　optimization　design　of　compliant　mechanisms.　©2010　Journal　of　Mechanical　Engineering.