The characterization of the regional ground water flow system is very important to high-level radioactive waste geological disposal. The Beishan area, located in northwestern Gansu Province, China, is selected as a potential site for disposal repository. The area includes about 100000 km2 and has complicated hydrogeological conditions, which greatly increase the computational effort of regional ground water flow models. In order to reduce computing time, parallel computing scheme was applied to regional ground water flow simulation. Models with over one million cells were used to simulate how the faults and different recharge conditions impact regional ground water flow, both in steady and transient state. The results of this study provide regional ground water flow information for site characterization of the potential high-level radioactive waste disposal. The characterization of the regional ground water flow system is very important to high-level radioactive waste geological disposal. The Beishan area, located in northwestern Gansu Province, China, is selected as a potential site for disposal repository. The area includes about 100000 km2 and has complicated hydrogeological conditions, which greatly increase the computational effort of regional ground water flow models. and different recharge conditions impact regional ground water flow, both in steady and transient state. The results of this study provide provide ground ground water flow information for site characterization of the potential high-level radioactive waste disposal.