The invention discloses an identification system and an identification method for a frequency domain of a servo system, wherein the identification system comprises the components of a motor parameter reading-in module which reads rated current of a servo motor in a servo system and a reference load inertia ratio of the servo motor; an amplitude adaptive random testing sequence generating module which generates an amplitude adaptive random testing sequence; a speed open-loop testing module acquires the motor rotating speed of a testing structure; a frequency characteristic solving module which acquires the frequency characteristic of the servo system; and a frequency model identification module which establishes a to-be-calculated frequency model and approximates the frequency characteristic that is obtained by the frequency characteristic solving module through the to-be-calculated frequency model. The identification method through the frequency model has beneficial effects of higher reliability and higher accuracy relative to prior art.