The　combined　three-section　crossbeam　is　an　important　component　in　the　heavy　gantry　CNC　milling-lathing　machine　tool　and　the　dynamic　characteristics　are　key　precision　factors　for　the　machine　tool.　Three　sections　of　the　combined　crossbeam　are　bolted　by　large　industrial　bolts　and　the　influence　of　bolted　joints　should　be　evaluated　in　the　dynamic　analysis　of　the　combined　crossbeam.　The　dynamic　characteristics　of　the　combined　three-section　crossbeam　were　extracted　by　the　modal　experiment.　The　FEM　of　the　monolithic　crossbeam　was　modeled　to　analyze　the　dynamic　characteristic　parameters.　The　comparison　of　the　analysis　result　and　experimental　result　were　shown.　The　experimental　result　matched　well　with　the　FEM　of　the　monolithic　crossbeam　without　bolted　joints.　As　a　result,　the　influence　of　the　bolted　joints　could　be　ignorable　in　dynamic　characteristic　for　the　combined　three-section　crossbeam.