Coal is an important energy fuel, and safe mining of coal is of great significance to economic stability. The mechanical properties of coal are very important to prevent the pores and fractures caused by mining and for the stability of the mine, as well as the coal and gas explosion disasters caused by mining failures. The macroscopic fractures are generated from a mesoscopic state. In this research work, a NanoVoxel-3502E X-ray three-dimensional microscope and the Deben in situ loading technology were used to carry out the uniaxial compression testing of coal and also to obtain the CT data under different strain conditions. The data were combined using three-dimensional visualization software AVIZO to extract the pore and fracture distribution characteristics of the coal sample and to analyze the evolution of the microstructure of the sample under the influence of axial stress. According to the obtained results, small fractures appeared in large numbers when the axial force increased from 20 to 732 N, and the fractures became narrow and long at 431−732 N. At 732 N, the average value of the throat equivalent radius and the average value of the throat area were the largest. When the axial force reached the peak, a complex fracture network was formed, while the volume and area of the fracture increased at the fastest rate; most of the isolated pores disappeared after the peak.
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