The microstructure of coal determines its mechanical behaviors under various loading conditions. In this study, DEM models were proposed based on the grain-scale reconstructed coal structure. The obtained SEM images were digitalized and converted to the binary digital images, and then introduced to build DEM numerical models reflecting the different microstructure characteristics of the coal. Finally, numerical simulation of biaxial compression were performed on each coal sample model. The results showed that different coal samples have different damage patterns under biaxial compression depending on their unique microstructural features. The initiation and propagation of tensile cracks are the main factors for the deformation and failure of coal samples. Near the peak strength of the axial stress, the average contact force between particles is the largest and the crack propagation speed is the fastest. In addition, high confining pressure and loading rate will promote the deformation and failure of coal samples. (C) 2019 Elsevier B.V. All rights reserved.