The invention discloses a flange gasket and relates to the technical field of seal gaskets. The flange gasket comprises a flange gasket body. Eight U-shaped grooves are annularly and evenly distributed on the flange gasket body 1. The upper end face of a rubber block is an inclined face. The high end of the inclined face is away from the axis position. A spherical bulge is arranged in the middle of the inclined face. Spherical cavities are formed in the inner side of the spherical bulge. An annular bulge is arranged on the upper end face of the flange gasket body. The axis of the annular bulgeis the same as that of a metal ring. The inner side of the annular bulge is an annular cavity. The annular cavity communicates with the eight spherical cavities through eight communicating channels.The U-shaped grooves formed in the flange gasket are used for installing studs, openings of the U-shaped grooves are outward and can discharge liquid accumulated in the U-shaped grooves, and rusting of the studs is avoided. In addition, the spherical cavities formed in the flange gasket body and the annular cavity form an integral structure through the communicating channels, the annular cavity becomes larger under the condition of pressure, and leakproofness of the flange gasket is improved.