Abstract: To study the hydraulic characteristics of rough rock fracture, a pressure model based on the lattice Boltzmann model is established. Based on simulations of three groups of different specimens (flat smooth fracture, rectangular non-match fracture and random gap width fracture), the relationship between the flow and the average gap width can be fitted. The research results show that under the calculated 10 kinds of working conditions, the flows of the three groups of fractures are close to the laminar ones. Only in parallel smooth cracks, the relationship between the flux and average gap width is approximately a cubic one, and that for rectangular mismatching crack and random gap width fissure shows a super-cubic relationship. Changing the average gap width and import and export pressures may lead to the variation of relationship between the flux and average gap width. In the meantime, the later can also cause the presence of cubic relationship between them.