Abstract: In order to study the influence of magnetic pull on the dynamic characteristics of motorized spindle with different structures, according to the mechanical equation of magnetic pull force of the motorized spindle, the finite element analysis model of the motorized spindle is established, two-way coupling calculations of magnetic field and mechanical field is carried out, the dynamic characteristics of the motorized spindle with different motor positions are studied, the dynamic characteristic curve is obtained. At the same time, the motorized spindle is tested to verify the rationality and correctness of the finite element model and the analysis method. Results show that the motor position of the motorized spindle will affect the motion stability of the motorized spindle, and the motor in the middle of the bearing of the spindle will run more stable than the motor at one end of the spindle; under the condition of test error and model simplification error, the total displacement of the axis trajectory calculated by the theory is slightly smaller than the measured value, the rationality and correctness of the finite element model and algorithm are verified preliminarily.