This paper analyses the rock fracture problem of Brazil disc split tests by using an improved DDA method. By incorporating a new rock fracture law and the discretization approach, the improved DDA can be used to simulate crack propagation during the rock fracture process in a two-dimensional plane stress state, such as the crack propagation in Brazil disc split tests. A numerical example of simulating the Brazil disc split tests for verification has been computed using the proposed DDA method. The simulated result agrees well with those obtained from the experiment, which proves the effectiveness and accuracy of the proposed DDA method. Meanwhile, the Brazil disc split test under different loading rates is performed systematically to investigate the external influences on rock fracturing. The result shows that the improved DDA can be well used for simulating the two-dimensional dynamic rock fracture problems in engineering.