To discriminate between earthquakes and explosions, spectrum range selection and spectrum resolution are sensitive and important constraint factors for recognition rate. This paper proposes a feature extracting algorithm for seismic wave spectrum analysis by using Chirp-Z transform. Initially by Fourier transform (FFT), overall spectrum layout is acquired. Upon this overall layout, seismic signals, suitable frequency range in the spectrum which contains most discriminative information are selected, then the proposed Chirp-Z transform is applied to get finer resolution spectrum, and at last more accurate spectrum features corresponding to different type signals are achieved. This algorithm is very useful to improve the accuracy of the discrimination problem and experiment results show its priority to classic Fourier transform.