Abstract: The cavitation erosion behavior of Inconel 718 nickel-based superalloy and 316L stainless steel were investigated using an ultrasonic vibration apparatus. The eroded surface, microstructure evolution and phase analysis were also observed and explored through scanning electron microscopy, cold field emission scanning microscopy and high-resolution X-ray diffractometer. The results show that Inconel 718 had excellent cavitation erosion resistance, its cumulative mass loss in 600 min and incubation time was about 1/3 and 2 times than that of 316L, respectively. At incubation period, the eroded region of Inconel 718 mainly located on the grain boundary, twin boundary and other interfaces. In contrast, 316L behaved marked plastic deformation which was characterized by the surface fluctuation. During the acceleration period, it was noted that the notable increase of mass loss about Inconel 718 was caused by the gradual spalling of material with propagation of microcracks on cavitation surfaces. At the same time, the remarkable mass loss of 316L was contributed to the continuous formation and merger of numerous pits on cavitation surfaces. After cavitation erosion for 120 min of Inconel 718, obvious deformation twins were observed on the eroded surface. Compared with the metallographic morphology before cavitation, the number of the deformation twins significantly increased.