The discretized virtual internal bond (discretized-VIB) is a newly developed lattice bond method for modeling nonlinear elasticity. Different from the usual lattice model, the discretized-VIB consists of unit bond cells. Each unit cell has a finite number of bonds and can have any geometry. These features make the discretized-VIB quite suitable for modeling rock with a meso-structure of grains. Because the unit cell is directly characterized by the particle force-displacement constitutive relation derived from the micro-bond potential, the discretized-VIB can directly simulate the dynamic fracture behaviors of finite deformation without any external fracture criterion. In the present paper, the heterogeneity of rock is accounted in discretized-VIB by assuming that the Young’s modulus of unit cell complies with the Weibull distribution law. By simulating a typical dynamic fracture branching example, it is suggested the present method can simulate dynamic fracture initiation, propagation and branching process without separate fracture criterion. It can capture the main characteristics of dynamic fracture in rock. The results also show that rock heterogeneity influences the trajectory of dynamic fracture. The more heterogeneous the rock, the more tortuous the fracture trajectory becomes.