Aiming　at　solving　the　load　bearing　deformation　compensation　problem　of　long　span　and　heavy　load　crossbeam,　this　paper　presents　an　approach　by　estimating　the　arch　curve　to　improve　the　machining　precision　of　the　heavy　machine　tool　product.　The　estimating　load　curve　was　obtained　based　on　the　finite　element　analysis　method,　and　then　we　get　the　arch　curve　which　would　been　verified　through　measurement　experiment　in　the　next　step.　This　study　can　provide　theory　and　technology　guidance　for　the　load　curve　design,　structure　design,　optimization　and　reverse　deformation　processing　of　the　long　span　and　heavy　load　crossbeam.