The utility model discloses a pipeline flow flange seal heat preservation device, the pipeline flow that is particularly useful for among the offshore oil platform is used. This sealed heat preservation device includes the body, and it is seal for pipe joints covers that the middle part of body is flange seal cover, both ends, is equipped with viewing window above the flange seal cover, the body through water -tight zipper to closing, the internal diameter of seal for pipe joints cover conforms to with the external diameter of pipeline, its interior surface paste joint strip. Can keep warm to the flange seal among the pipeline process flow, especially the flange seal of pipeline flow keeps warm among the offshore oil platform, can prevent that marine salt fog or rainwater from getting into flange joint department, the operating condition of being convenient for the installation and dismantling and can survey the flange, the corrosion of flow flange joint department has been avoided, the problem of the flange when patrolling and examining broken tearing open hard behind the heat preservation resume and increase the maintenance cost is solved, and production costs are effectively reduced, and a work efficiency is increased, fine result of use and economic benefits have.