Ultra high speed centrifugal grinding machine is a new type of grinding machine， compared with the traditional ultrahigh speed grinding machine，its cubic boron nitride (CBN) grinding wheel is equipped with a motorized spindle. Three-dimensional (3D) model is established based on the geometry of motorized spindle. The simulation analysis was carried on using ANSYS. Whether there was interference， situation of key components of stress and stiffness in the model were detected. Analysis is carried on the influence of different rotational speed of spindle on stiffness and the stability of the system.