To improve the tracking accuracy of an electromechanical actuator servo system, the methods to identify and compensate the noninearities of friction and backlash were put forward. The mathematical models based on the LuGre friction and the hysteresis backlash were established for the electromechanical actuator servo system with position loop and speed loop controllers. According to the identified nonlinearity models, the friction was compensated though a feed-forward method, and the backlash was compensated simultaneously though an inverse model as well. The experiments indicate that the maximum position tracking error of system after compensation decreases from 0.166° to 0.096°, and the maximum speed tracking error decreases from 2.723 r/min to 0.393 r/min when the given signal is sine wave with an amplitude of 1° and a frequency of 2.5 Hz. It concluds that the friction and backlash models can be accurately obtained by the proposed identification methods, and the tracking accuracy of the electromechanical actuator servo system can be improved through nonlinearity compensation on the basis of the proposed models.