During manufacturing Cu-30Ni alloy condenser tube, the defects such as crack were fatal to the successive processing operations. The cause of failure induced by manufacturing defect in Cu-30Ni alloy tube was investigated by employing nondestructive penetrative test technology, optical microscope, scanning electronic microscope with energy-dispersive spectrometer and tensile properties test. It was found that cracks including long continuous crack, short discontinuous crack and chevron crack were the main problem caused the manufacturing failure at the industrial production line. There were three principal evolutions of cracks, i.e., inter-granular, trans-granular and the combination of them. These cracks could decrease the elongation by about 10% in comparison with that of good tube, whereas it had no effect on yield ratio. From fractography around the crack, it was seen that there appeared to be different inclusions with different compositions. These inclusions were responsible for the manufacturing failure during the processing of the Cu-30Ni alloy tube.