Abstract: The present research objects of the grouting numerical simulation of fractured rock mass focus on a single facture or two-dimensional fracture network, while the randomness of aperture distribution has been seldom considered. Aiming at above problem, a three-dimensional stochastic fracture network model for grouting numerical simulation coupled with the randomly distributed aperture and grout hole is firstly established, based on the Monte-Carlo method. Then, the three-dimensional distinct element code (3DEC) is employed to simulate the grout diffusion process with a multistage water-cement ratio in the fracture network, and the distribution characteristics of pressure field and flow field of unit width are analyzed. Finally, the bedrock curtain grouting process of a grouting hole in a hydropower station is taken as a case. Research results show that:the pressure attenuation trend of cement grout is nonlinear from the grouting hole, in the vicinity of which the pressure decreases the fastest; because of the water cement ratio becoming thicker gradually, slurry flow rate decreases as a ladder pattern with the increase of grout time. Furthermore, comparing the simulation value with the actual measuring value of the grouting quantity and time, the relative errors are -17.11% and 3.11%, respectively, which verifies the availability of the method.