A theory on the wave drag as the Rankine ovoids moving horizontally, uniformly and rapidly in uniformly vertical stratified fluid (or ocean) is presented. A mass source resulting from the theory in a uniform fluid is used to model a hydrodynamic interaction between the Rankine ovoid and stratification. Theoretical results show that there exists an asymptotic state of the drag in supercritical regimes where internal Froude numbers are large. When the Rankine ovoid reduces to a sphere, the result we obtained is in good agreement with the previous theoretical and experimental results. An experiment on the elongated Rankine ovoid is also carried out to validate the theoretical results.