In order to study the static stiffness of high speed motorized spindle,using DH3818 static strain gauge,the relationship between motorized spindle static stiffness and the force on the motorized spindle was studied.Using static strain gauge and force sensor,the radial rigidity and axial rigidity of 1.5×104 r/min motorized spindle and 6×104 r/min motorized spindle were tested when the spindles were in stable state.The high speed motorized spindle static stiffness was inversely proportional to the end deformation.The comparative analysis to the 1.5 ×104 r/min motorized spindle axial stiffness and radial stiffness shows the motorized spindle radial stiffness is far greater than the axial stiffness.The comparative analysis to the 1.5 ×104 r/min and 6×104 r/min motorized spindle radial stiffness shows the motorized spindle with lower maximum speed has big stiffness than that with high maximum speed.Because low stiffness has impact on CNC machine tool performance,so improving the static stiffness of the motorized spindle can also improve the performance of the machine.