Abstract: The cyclic loading and unloading tests of two kinds of marble and one kind of sandstone were carried out under the direct tension condition by using the microcomputer controlled electronic universal testing machine, and the acoustic emission characteristics and spectrum characteristics of rock damage were analyzed.The results show that in the cyclic loading and unloading tests, three kinds of rocks show obvious Kaiser effect, the rock memory lags behind at low stress and the rock memory is slowly ahead at high stress.As the number of cycles increases, the AE intensity of rock gradually increases, Felicity ratio gradually decreases, and the elastic modulus gradually decreases.By comparing the relationship between the Felicity ratio and the number "1", the stress state of rock can be judged.When the Felicity ratio is far greater than 1, it indicates that the rock loading is far from the bearing limit, and when the Felicity ratio is close to 1 or less 1, it indicates that the rock loading is close to the bearing limit and the stress state is closer to the failure stress.In the process of rock tensile fracture, AE signals always have low-frequency, medium-frequency and high-frequency signals, and the proportion of low-frequency signals is greater than that of medium-frequency and high-frequency signals.By analyzing the spectral characteristics of AE signals, four AE microscopic mechanisms exist in the tensile fracture of rocks.The first type is the frictional acoustic emission mechanism caused by intergranular slip and particle friction, with small signal energy and low main frequency.The second type is the ruptured acoustic emission mechanism caused by the expansion of new cracks, with medium signal energy and high main frequency.The third type is the frictional acoustic emission mechanism caused by little cracks' friction, with low signal energy and medium main frequency.The fourth type is the mixed acoustic emission mechanism of macroscopic crack expansion and friction, with large signal energy wide signal frequency band, which the high frequency and low frequency signals coexist.The AE characteristics of crack propagation obtained in this paper provide a basis for the failure mechanism and monitoring of rock under tension condition.