Abstract: In order to study the damage and cracks development of coal-rock combination under different confining pressure and the relationship among them, the PFC^2D software was used to simulate compression of coal-rock combination under different confining pressure. The results show that: with the increase of confining pressure, the failure of the combination is changed from brittle failure to ductile failure, and its direct cause is the rapid development of shear cracks. The main failure of the combination is the shear failure of the coal body, and the shear crack develops rapidly near the tensile surface, resulting in shear failure of the combination.