In　this　paper,　the　finite　dynamic　element　of　triangular　bending　plate　is　expressed　in　frequency　expansion　form　of　a　single　impedance　matrix,　hence　the　formulation　of　finite　dynamic　element　is　simplified　significantly.　If　only　terms　up　to　frequency　square　are　retained,　the　free　vibration　equation　based　on　the　impedance　matrix　expansion　can　be　identical　with　the　conventional　finite　element　equation.　For　a　triangular　bending　plate　element,　the　impedance　matrix　expansion　terms　to　the　second　order　are　derived　and,　as　an　illustrative　example,　applied　to　the　calculation　of　the　first　six　natural　frequencies　of　a　cantilever　triangular　plate.