In order to properly handle the water inrush and flooding accidents caused by complicated geology, rapid groundwater development with excessive recharging, improper excavation and construction methods, inadequate technology and management measures, this paper takes the inrush and flooding at the auxiliary shaft in the 1# shaft of Gaoligongshan Tunnel of Darui Railway as an example, and introduces the water sealing method with modified cement slurry under hydrostatic pressure in detail, which is used to deal with flooding accidents. A set of parameters apply to the cases such as tight construction period, deep flooding, complex geology, excessive and fast water supply are put forward, which can provide reference for the flooding treatment with water depth exceeding 600 meters.