Abstract: Based on the actual manufacturing process of submerged-arc weld spiral pipe and from the point of view of welding metallurgy and the non-weld stress factors, the author analyzes the root causes for cracking of inner weld seam of submerged-arc weld spiral pipe, concluding that actions be taken to eliminate all the non-weld stress factors involved for the purpose of preventing or eliminating the said inner weld seam thermal cracking.