The utility model is suitable for a nuclear power station overhauls technical field, provides stifled isolation structure of online ice of nuclear power station pipeline, its include the internal flow have liquid medium wait keep apart pipeline, demountable installation on waiting to keep apart the pipeline and waiting to keep apart the pipeline periphery and be formed with the isolation anchor clamps that hold the chamber and fill and form the refrigerant of ice berg in holding the intracavity in order to be used for cooling off liquid medium in waiting to keep apart the pipeline to freeze, keep apart to have on the anchor clamps supplying the refrigerant to get into the import of holding the intracavity. The utility model discloses it cools off and forms the ice berg to utilize the refrigerant to treat the liquid medium who keeps apart in the pipeline to can realize the local of nuclear power station pipeline under the prerequisite that does not influence the normal operating of nuclear power station unit keeps apart. It is used for realizing that the local structure overall structure who keeps apart of nuclear power station pipeline is fairly simple to quick installation can be realized and dismantle with quick that it is very convenient to operate, thereby does benefit to the cost of overhaul that reduces the nuclear power station, and the fail safe nature that the reinforcing nuclear power station overhauld the in -process is done benefit to.