Abstract: The article makes a simplified introduction on the limitations of conventional strength theory. It points out that the abundant safety of high strength steel tough ness is an important factor which should be considered in material sellection of pipeline design and it also introduces such experi-enced formula that could determine the starting fracture and ending fracture of non-periorated crack. At the end of article, the author uses those prac-tical examles to explain the teasibility of such damage-safety design theory.