Abstract: It can remove residual welding deformation effectively to use technology of restraint welding and reverse deformation.But,it is very difficult to calculate values of restraint,restraint length and reverse deformation accurately,because of the complication of stress fields in welded structure.Study showed that angle deformation of T joint is changed along the welded seam length.In the case of a short welded seam,it is approximatele constant.Under restraint welding,the material is plastic in the place of welded seam and nearness.But in the distance the material is elastic.By theory of elasto-plastic bend,this paper provides the model to calculate out-of-plane restraint to remove angle deformation in T joint.The values of the critical restraint length,limit restraint and reverse deformation have been calculated.The results of tests show that the calculation method is effective.The method can be generalized for the case of a long welded seam.