Abstract: Analyzed in the article is the reasons for the leakage failure of the sample from a certain refined oil pipeline.It is found that the leakage-causing crack is located at the arc-starting and arc-ending points of the girth weld.As a result it is identified that the main reasons for the said leakage failure of the steel pipe are the existence of welding thermal crack in the girth weld,and the poor formation of the inner surface of the girth weld,and thus during a long time service,affected by both internal and external loads,the welding thermal crack near the weld beading gets the stress concentrated,and then expanded,which inevitably leads to the leakage failure of the girth weld.