The initiation and development of hydraulic fractures were simulated using the Particle Flow Code (PFC^2D) from the meso-prospective, and some influencing factors were analyzed. Results showed that the generation and propagation of crack can be simulated practically. The hydraulic fracturing would occur if contact bonds lying between the particles fail around the initial crack tip. It was also illustrated that the value of initiation pressure is influenced by the relative length of initial crack, permeability of rock mass and the loading rates of water pressure. With the increase of initial crack length, the initiation pressure decreases. And it would increase significantly if the permeability of rock mass increases. As water pressure loading rates accelerate, the initiation pressure would be reduced. These conclusions were in good agreement with theories, which showed the feasibility of simulating the hydraulic fracturing of fractured rock mass with particle discrete element method.
