Abstract: In order to thoroughly explore the internal response characteristics and the catastrophic behaviors of rock mass caused by unloading in deep excavation process,the self-developed triaxial acoustic emission acquisition system is used to conduct the triaxial unloading tests of sandstone with different unloading rates and different confining pres-sures. Seismic statistics method is used to analyze the parameters such as absolute energy E and waiting time δ. The re-sults show that:① the probability density function of absolute energy released in the unloading follows a power law dis-tribution well in the range of 101 aJ to 104 aJ. ② With the decrease of unloading rate,the possibility of small energy events occurrence is increasing. There is a similar trend with the increase of confining pressure in the same unloading rate. ③ The “ after-shock” of acoustic emission events meets the same linear relationship under different confining pressures and unloading rates,and it is not affected by the fluctuation of the “ main shock” events energies. ④ In a short time interval range (less than 0. 1 s),the power exponent is not affected by confining pressure and unloading rate. For a long interval range (greater than 0. 1 s),the power exponent fluctuates in the range of 1. 3 to 1. 9. The dis-tributions of waiting time for different energy thresholds show universality well.