Plastic gasket with good sealing effect

The utility model discloses a plastic gasket with a good sealing effect, which belongs to the technical field of plastic gaskets and comprises a gasket body in a circular ring shape, a first annular groove is arranged on the outer wall of the gasket body, second annular grooves are arranged on two opposite end faces of the gasket body, and the first annular groove is communicated with the second annular groove. The axis of the second annular groove coincides with the axis of the gasket body. The expansion ring is installed in the first annular groove in the outer wall of the gasket body, the supporting rings are installed in the second annular grooves in the two end faces of the gasket body, when the gasket body is fatigued and a fastener is screwed, the expansion ring is extruded to protrude out of the gasket body due to the fact that the interior of the expansion ring is hollow, and therefore the gasket body is prevented from being damaged. The supporting ring acts on the edge of the inner wall of the gaske