The rear motorized spindle is directly driven by rear motor and equipped with water cooling system. Due to the good heat dissipation condition of the motor, low temperature rise of the bearing, small thermal deformation of the spindle, high speed and torque transmission, good rigidity and compact mechanism, the production efficiency of the machine tool and the processing quality of the workpiece can be greatly improved. The spindle has the functions of automatic release of broach,accurate control of rotation speed, accurate stop and central inner cooling.