Abstract: In this paper, the fracture behaviour of rock under dynamic loads was studied by using the Hopkinson bar method. When the stress amplitude is higher than the initial fracture stress, the rock specimen fractures and the stress amplitude attenuates. A maximum limit of the energy which can be transmitted through a rock specimen was found. This limit is essentially a stress amplitude value over which higher stresses can not be transmitted. The degree of brittleness of rock was determined by using the attenuation of the wavefront in a fracturing specimen.