The article presents results of investigation of residual stresses for multi-layer circumferential welds of oil and gas pipelines. The research was carried out on a designed and manufactured testing equipment for the experimental determination of the stress state parameters in the zone of multi-layer welded joints of pipe segments with the external diameter of 1020 mm and the wall thicknesses of 9.5 mm, of 14 mm, and of 22 mm which were made of carbon steels of different quality (13G1S, 13G1SU, 17G1S and 17G1SU). Determination of residual stresses in the zone of multi-layered circumferential welds of pipe segments was carried out by means of the method by the electronic speckle-interferometry and by the method of magnetoelasticity. On the basic of analysis of the obtained graphic dependences, the recommendations for engineering practice are suggested.