The invention discloses a method for detecting the dynamic characteristics of a fixing combination portion of a machine tool. In the method, the fixing combination portion is taken as a virtual material with equal section, and the virtual material and the parts at two sides of the fixing combination portion are in rigid connection. Through detecting the parameters of elastic modulus, the Poisson ratio, the density, the yield strength, the hardness and the geometric size of parts constituting the combination portion part, the elastic modulus, the Poisson ratio and the thickness of the virtual material are obtained, the virtual material and the two parts at two sides of the fixing combination portion are in rigid connection; the three calculated parameters of the elastic modulus, the Poisson ratio and the density of the virtual material are input to a finite element software, and some dynamic characteristics (such as, mode of vibration, natural frequency, displacement, and the like) of the complex parts of the combination portion are detected. The relative error of the theory and the natural frequency of the first 6-step of an experiment is (-10 to 10) %, while the maximum relative error of the traditional influential Yoshimura model is about 4 times that of the virtual material mode. When damage experiments are not directly allowed for some precise digital control machine tools, and the experimental cost can be greatly reduced by using the predictor method of the theory.