Abstract: An acoustic emission inspection for a 2 000 m³ spherical tank with super active crack defects is carried out. The characteristics and sources of crack acoustic emission signal in pressure rising and maintaining process are analyzed. Using nondestructive testing methods such as TOFD and UT, the type and geometry size of the defects were determined, and the reason for the defect formation was combined. Finally, the evaluation of the safety performance of the spherical tank was completed.