The utility model relates to a sealing ring for leak of a flange, the sealing ring with a T shape section is made of rubber or plastics, and the sealing ring is mutually inserted with an annular opening. A convex tongue is arranged on the center of one end of the sealing ring for leak of a flange; a flute is arranged on the center of the cross section of the sealing ring in the inner direction; the thickness of the flute can be changed when the flute is embedded to the gap of the flange, the flute is easy to be embedded into the gap of the flange, and the flange is held by the expansive force of the sealing ring; the flange is unease to fall off to cause dust can not enter into the gap between the flanges. The utility model has the advantages of simple structure, convenient use and beautiful appearance, and the gap of the flange can be quickly sealed.