In our city, 75000 m3 Wet Gasholder generated coal gas leak during the work due to the crack of tower wall , which directly endangered life and property security of the people. In the paper, the cause on the failure of gasholder was made much conjecture. Firstly, physicochemical examination and mechanics property on gasholder material component were conducted. Weld conditions between pillar and joist were observed on spot. Secondly, stress of gasholder was analyzed by using finite element code. Thirdly, field tests on the vibration of gasholder were also carried out by means of vibration apparatus. Finally, the principal cause of the failure is determined, and some propose on the maintenance and construction of gasholder is provided.