Abstract: The military H62 brass tanks produced by a factory were put into storage after hydrostatic test, and cracked after a period of time. The causes of cracking on brass tank were analyzed by means of chemical composition analysis, metallographic examination, hardness test, scanning electron microscope analysis and energy spectrum analysis, combined with production process and field conditions. The results show that the brass tank was not annealed after mechanical drilling and welding, which led to stress concentration in weld seam. The subsequent hydraulic test provided a humid environment, causing the dezincification of β phase in the microstructure, which led to the decline of mechanical properties of brass, and finally stress corrosion cracking occurred.