In　this　paper　a　new　concept　of　impedance　matrix　for　finite　dynamic　element　is　proposed,　hence　there　is　no　need　to　derive　mass　and　stiffness　matrix　expansion　terms　separately　and　the　formulation　of　finite　dynamic　element　is　simplified　significantly.　For　a　rectangular　bending　plate　element,　the　impedance　matrix　expansion　terms　to　the　second　order　are　derived,　with　which　the　natural　frequencies　of　a　square　cantilever　plate　served　as　an　illustrative　example　are　calculated.