Aiming　at　solving　issues　of　load　bearing　deformation　compensation　and　sympathetic　vibration,　this　paper　takes　a　large　span　and　heavy　load　crossbeam　of　a　domestic　heavy-type　numerical　control　milling　planer　for　research　object,　the　final　purpose　is　to　improve　machining　precision　and　stability　of　the　heavy　machine　tool　product.　The　load　curve　considering　the　influence　of　columns　deformation,　natural　frequency　and　vibration　model　are　obtained,　respectively　by　the　dynamic　and　static　simulation　analysis　of　the　crossbeam　with　the　finite　element　analysis　method.　Then,　the　modal　analysis　results　are　verified　through　the　model　experiment.　Lastly,　this　paper　presents　an　approach　by　estimating　the　load　curve　to　improve　machining　precision,　points　out　the　weak　links,　and　provides　guidance　for　crossbeam　structure　design,　optimization　and　reverse　manufacture.　©　(2011)　Trans　Tech　Publications.