The utility model relates to a leakproof sealing device, particularly an elliptic rubber sealing ring, which is formed by that a ring body is rounded. The ring body of the rubber sealing ring has an elliptical cross section. A short shaft of the elliptic cross section is coincident with the radial line of the ring body of the rubber sealing ring. The realization of a typing angle with a large range for being selected during manufacture, no damage on the sealing surface of the work piece, easy mold release, small amount of precompression, etc., exists. The utility model has the advantages of good sealing effect, strong reliability, long service life, low manufacture cost and maintenance cost, etc., and is particularly suitable for the leakproof sealing of fluid reciprocating moving parts.