In order to get the structural dynamic of the high speed ball screw driven servomechanism, a hybrid modeling method was proposed. The proposed model took the axial, torsional and bending vibrations of the screw into consideration by the Euler-Bernoulli beam elements with axial and torsional theories. The servo subsystems and the other more rigid components were modeled by the lumped parameter method. The flexible ball screw feed drive servomechanism was proposed, including the friction, backlash and the cutting disturbance. Compared with the experimental results, the hybrid model could accurately capture the structural dynamics of ball screw drives. Numerical simulation indicated that the nonlinearities of friction and backlash could cause velocity fluctuations at the low speed. The torsional and axial vibrations made the servo system unstable, especially in the high speed application.