Abstract: After being shielded arc welded，the steel pipe as in the extrusion state has to be running for a speci-fic distance so as to ensure that the pre-welded tube has enough strength against the elastic force effect. Elaborated in the article is the method for making design for this purpose. Based on the analysis of the weld stress state of the tube that has run through the self-holding distance，the weld’s cooling temperature and time are deduced，and then the said extrusion distance held by the pre-welding/weld joining device is determined. As the said distance is properly specified and held，the weld can be cooled down to a certain extent to have sufficient strength against the elastic force effect，while it is possible to avoid the troubles like weld offsetting or the extrusion roll’s failure to be pressed down due to the over large extrusion force as caused by the over-long extrusion distance.