In order to obtain frequency characteristic of an electrohydraulic servo turntable system, Chirp signal was adopted as excitation. In order to solve the problem of serious distortion of frequency characteristic curves derived directly from Fast Fourier Transform (FFT) of original timedomain sample signals, original timedomain sample signals were processed successively by low pass filtering, wavelet packet denoising, and amendment of phase hop at high frequency, and by FET. Finally, smooth filtering is used to acquire frequency characteristic curves, which really satisfy the requirement of system debugging and performance assessment.