In order to study the distribution, fractal characteristics and instability failure mechanism of coal-rock assemblages under different loading rates, uniaxial compression tests of fine sandstone-coal (FC), coarse sandstone-coal (GC) and fine sandstone-coal-coarse sandstone (FCG) were carried out under 0.001mm/s, 0.005mm/s, 0.01mm/s, 0.05mm/s and 0.1mm/s loading rates. The results show that: 1) at the 0.001mm/s rate, the particle size of the broken coal is small, which is a complete and full failure, and the failure type belongs to plastic failure. Under the 0.1mm/s loading rate, the size of the failure fragment is the largest and the shape is irregular, which is incomplete and inadequate, and the failure type belongs to brittle failure. The influence of loading rate on the failure of specimens is mainly shown in the degree of fracture development, the particle size of failure blocks, the number of failure blocks, the rate of energy release, the form of failure and the mechanism of instability. 2) the sample fragments have obvious classification characteristics. With the increase of loading rate, the number of fragments < 20mm decreases gradually, and the fragmentation degree of specimens decreases, and the length / thickness values of three kinds of specimens increase at first and then decrease with the decrease of fragment size. Under different loading rates, the length / thickness values of the same particle size grade are as follows: 0.1mm/s > 0.05mm/s > 0.01mm/s > 0.005mm/s > 0.001mm. Increasing the loading rate will promote the growth of thin-shaped fragments. 3) at five loading rates, the particle size-quantity fractal dimensions of FC, GC and FCG composites are 1.53335~0.548,1.26769~0.25999,1.44565~0.46054, respectively. The granularity-quantity fractal dimension decreases with the increase of loading rate, and the higher the loading rate is, the smaller the fractal dimension is. The particle size-mass fractal dimensions of FC, GC and FCG composites are 2.35~1.48,2.36~1.34 and 2.34~1.58, respectively, and the particle size-mass fractal dimensions decrease with the increase of loading rate. 4) according to the failure form of coal-rock assembly, the energy transfer mechanism of the failure process is analyzed. With the continuous loading of the assembly, the coal component is the first to be destroyed, and the released energy is directly transferred to the rock component. If it reaches the energy storage limit of the rock component, it will lead to the failure of the rock component. The energy transfer mechanism in the failure process of coal-rock assemblage well reveals the lag phenomenon of rock component failure.