Abstract: The welding thermal elasto-plastic stress-strain cycles diagram (shortly WSS diagram) describes the welding stressstrain relation on the whole.The stress-strain cycle in every area is the necessary part of the WSS diagram.The stress and strain relations of the points with different distances from the weld centerline on the specimen were investigated.The states of stress and strain of some point on the specimen during the welding process could be derived.On the basis of these results, the stress and strain relation in the each area of WSS diagram can be derived, and the diagram is described quantitatively, which make it easy to understand the WSS diagram.The results showed that the longitudinal stress-strain cycles are different in the different areas in the diagram.During the cooling process, weld and the zone nearby are in the unloaded states.