Based on power spectrum estimation, closedloop indirect identification method is proposed to deal with system identification of servo-valve controlled even hydraulic actuators, and its identification accuracy has been analyzed using different data lengths, windows, overlaps, segments and sensor resolutions. Firstly, an improved chirp signal is used to stimulate servo-valve controlled even hydraulic actuators. Then, open loop frequency characteristics of actuators are identified by using above method with measured input and output data. Finally, identification accuracy analysis using different signal processing is carried out through numerical simulation. The simulations results show that higher parameter identification accuracy can be obtained by using higher resolution sensor, longer data length, 2 segments and hamming window.