Abstract: An investigation was done on the coupling transversal cracking accident of super 13Cr steel premium connection tubing,and crack macro analysis,fracture analysis,chemical compositions analysis,metallographic examination and mechanical properties test were done to the cracking coupling and un-cracked tubing.The results show that t the coupling transversal cracking resulted in failure of the metal to metal seal,and then tubing leaked from metal to metal position and coupling cracking position.And the tubing coupling cracking was related to the original crack and high yield strength.