Abstract: In order to reveal the relationship between the relative quiet period of acoustic emission as a precursor to the damage of rock materials and their internal grain sizes, uniaxial compression-acoustic emission tests were carried out on rock-like materials made of high-purity quartz sand of four grain sizes as aggregate and cement as binder, and the damage variables of acoustic emission, RA value, r value, main frequency evolution of damage process of the rock-like materials of the four grain sizes, as well as the homogeneity of the specimens with coarse and fine grain sizes were analyzed to study and explore the relationship between the phenomenon of relative quiet period of acoustic emission and the grain size of rock-like materials. The results show that when the grain size is between 0.08 mm and 2 mm, the larger the grain size, the more prevalent and longer the relative quiet period of acoustic emission. The acoustic emission characteristics of rock-like materials are related to their rupture forms. In the early stage, it is mainly a mixed tension-shear hybrid crack. Then the tensile rupture decreases, and the final damage to the shear cracks are dominated by the acoustic emission of the relatively quiet period of the acoustic emission of the small energy shear micro-rupture. The specimens of relatively larger and larger particle sizes have high main frequency signals before the peak stress, and the high main frequency signals increase significantly in the relatively quiet period of the acoustic emission. The large particle size specimen with a grain size of 1.5-2 mm has the largest m-value and the highest degree of homogeneity. In contrast, the remaining three specimens are relatively small, and the degree of homogeneity fluctuates little with the change of the grain size. The research results provide a specific scientific basis for studying the relationship between the relative quiet period of acoustic emission from rock materials and their grain size composition.