In order to explore the vibration characteristics of the flexible shaft of the special milling machine for deep through hole keyway,combined with the structure of the machine tool,the Euler-Bernoulli theory was used to derive the radial vibration displacement response function model of the shaft,and the vibration displacement response curve of rotating shaft under single factor change of process parameters was obtained.The shaft vibration test was carried out,and the theoretical and experimental values of the shaft vibration displacement amplitude were compared respectively,the relative error was within 10%,which indicated that the theory and the experiment were in good agreement and the correctness of the derivation of the flexible shaft vibration theoretical model was verified.The model data and test results show that in the milling process,it is necessary to choose a small milling depth,a multi-tooth milling cutters with a small feed per tooth and a relatively small milling speed to make the milling process more stable and reduce the influence on the processing quality of the deep through hole keyway.The research results provide reference for the product design of machine tools.