Abstract: The mechanism and numerical simulation of hydraulic fracturing were summarized and the model on wedging action in weak link was proposed in the framework of the effective-stress method based on Biot’s consolidation theory.Then the smeared cracking theory was applied to simulate the process of hydraulic fracturing,while the fracture model and the calculation method were established to analyze the opening and expanding of hydraulic fracturing.As a case study,the process of hydraulic fracturing of Hyttejuvet Dam in Norway was analyzed and it was indicated that the fracture model and the numerical method could simulate well the behavior of hydraulic fracturing and could be applied to the safety assessment of earth dams.