The stress distribution in the forming process of high-grade spiral welded pipe was calculated by using three-dimensional finite element method.On this basis, press amount and post-forming stresses of spiral pipe with different steel grades and wall thicknesses were studied.The results show that the stress distribution after forming is not uniform.Except for the hoop stress near the free edge, the axial and hoop stresses on the inner surface are compressive stress distribution,while the axial and hoop stresses on the outer surface are tensile stress distribution.During the bending process, when the plate is under the inner roll in the three-roll bending area, the forming equivalent stress is the largest.After passed the forming roller, the elastic recovery of the plate occurs,the equivalent stress of the inner and outer surfaces decreases greatly,and the equivalent stress of the middle part of the plate decreases slightly.The equivalent stress does not change significantly when the plate passed the outer control rolls.With the increase of the steel grade, the appropriate press amount of the inner roll of the spiral pipe with the same diameter increases,and the hoop stress of the inner and outer surfaces of the spiral pipe with different steel grades increases with the steel grade.With the increase of the thickness of the forming plate,the appropriate press amount of the inner roll decreases,and the hoop stress of the delivery side decreases with the increase of the thickness,the axial stress does not change with the thickness of the plate.