In the process of excavation of hydraulic tunnels across the fault zone, the surrounding rock often lose steady and collapse, which will threaten the personal security. In this paper, a 3D model was established according to Hami pumped storage power station in Xinjiang. The variation of surrounding rock stress, deformation and plastic zone under the condition of full section excavation without support and timely support after excavation are compares and analysis. The calculated results indicate that the initial ground stress decreases along the axis of the tunnel in fault zone. In the case of excavation without support, the stress of surrounding rock in the fault zone will be released completely. The maximum deformation of tunnel vault along the axis is located in the left affected zone. In the case of timely support after excavation, the stress of surrounding rock in the fault zone will be partially retained. The deformation of tunnel vault is much smaller than that without support after excavation and the upper part of tunnel in fault zone basically has no plastic failure.