Rocks often experience not single load but combined load, such as combined compression and shear load. For studying the fracture process and the dynamic response of rock under combined compression and shear load, a bond contact model is established for discrete elements simulating the fracture process of a cylindrical limestone under combined compression and shear load, to observe the crack evolution and the load variation. Then, dynamic simulation is carried out to achieve the stress and displacement change of the compression-shear test machine. The results show that the vertical load does not remain unchanged but approximately linearly increases at the shear stage. When the vertical load reaches the maximum value, the cracks generate from both the upper and lower ends, propagate to the middle, and penetrate through the entire specimen. The vertical and horizontal loads will decrease rapidly. The maximum stress and displacement increase slowly at the compression stage, increase quickly at the shear stage, and decrease dramatically at the instant of fracture. The maximum stress, maximum displacement and contact pressure increase with the increase of the horizontal displacement.