The utility model discloses a water seal arrangement for nuclear power station white -out pipeline, including the type of falling U pipeline, the upper reaches and the total pipeline connection of containment white -out of the type of falling U pipeline, the type of falling U pipeline top is provided with vent line, vent line is last to be provided with the check valve that obstructs the fluid andmoved to vent line by the type of falling U pipeline top, the upper reaches of the type of falling U pipeline are provided with prevents that check valve that the flow stopping body moved to containment white -out house steward filamental flow by the type of falling U pipeline perhaps the upper reaches of the type of falling U pipeline with the ascending segment of the type of falling U pipe forms the linker of bottom intercommunication. The utility model provides a water seal arrangement for nuclear power station white -out pipeline can form the water seal at containment white -out house steward's shell outside the branch, prevent in the containment air in the same direction as white -out pipeline leakage outside the containment, consequently can reduce nuclear power plant safety shell leakage rate, guarantee nuclear power plant's operation and safety.