The work aims to predict the occurrence of cavitation during high-speed internal cooling milling and reveal the failure mechanism of tool and the damage mechanism of the machined workpiece surface by cavitation. By combining 3D numerical analysis with experiment, the numerical calculation was carried out based on the establishment of the closed flow field of high speed internal cooling milling. The high-speed internal cooling cavitation platform was built and experiment was conducted. The machined surface of the segment dworkpiece was measured by the roughness tester. The morphologies of machined surface of the segmented workpiece and the milling cutter were analyzed by scanning electron microscopy. Through simulation, the gas content of the flow field was about 10% when a hole with diameter of f60 mm and depth of 50 mm was milled with a f40 mm milling cutter at 14,500 revolutions per minute. The cavitation was predicted during high speed internal cooling milling. The roughness Ra of the wedge-shaped divergent zone was from 0.311 to 0.478 mm, while the roughness Ra of the wedge-shaped constriction zone ranged from 0.138 to 0.317 mm after the cavitation experiment. There were small pockmarks and sponge-like cavitation pinholes in the surface of the machined workpiece, while honey comb and fish scale-shaped cavitation pits appeared in the flake side of the milling cutter. Therefore, the existence of the cavitation phenomenon can be validated in the high-speed internal cooling milling process through both simulation analysis and experiments. The cavitation may appear on the flank surface of the internal cooling milling cutter and some machined surface of workpieces, and the cavitation in the flank of the milling cutter is much severer than that in the machined surface of the workpiece, which provides a basis for the study of cavitation mechanism in the process of high-speed internal cooling cutting.