In this study

acoustic emission (AE) experiments were carried out on saturated granite under uniaxial compression. Fast Fourier transform (FFT) was used to extract the spectrum parameters of AE signals such as dominant-frequency and secondary dominant-frequency. Furthermore

the ratio of the dominant-frequency to secondary dominant-frequency (F) was proposed to characterize the spectral characteristics of the AE signal and study the characteristics of AE spectrum in rock fracture process. The results show that the numbers of the dominant-frequency and secondary dominant-frequency bands of AE increase first and then decrease in the rupture process of saturated granite. Compared with the characteristics of the dominant-frequency distribution

the proportion of the low-frequency interval of the secondary dominant-frequency reduces

and the proportion of the middle and high-frequency interval increases. In addition

the total average value of the secondary dominant-frequency is about 5 kHz higher than that of the dominant-frequency. The distribution range of the dominant-frequency ratio (F) reaches the maximum at the elastic stage: 0