Finite　element　analysis　software　ANSYS　analysis　a　combination　sections　beam　which　has　contact　surface　and　a　integral　model.　Then　find　out　the　difference　to　identify　the　overall　model　and　the　parts　beam　dynamic　differences.　According　to　the　result　learn　the　contact　surface　how　to　influence　the　tools　dynamic.　It　can　offer　theoretical　and　practical　basis　for　design　and　structure　optimization.