The cavitation erosion behavior of ZQAl9-4-4-2 nickel-alum inium bronze in 2.4%NaCl solution was investigated by using a magnetostrictive – induced cavitation facility. The micrographs of damaged surface were observed by scanning electron microscope (SEM) and transmission electron microscopy(TEM). The results showed that the cavitation microcrack in the a phase adjacent to the k phase. They propagated and connected with each other in the a phases, resulted in the removal of a phases and detachment of the k phase from the matrix in the following test period followed. The microcracks tended to propagate parallelly to the eroded surfaces.