Abstract: 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.