This paper probes into mathematical properties of the parameter ellipsoid. Its result shows that under the restricted condition of both point gravity potential equality for pole and equator, the boundary surface with in the double layer ellipsoid limitlessly being tendency to the ellipsoid surface, the interior ellipsoid of the parameter ellipsoid tends to Maclaurin ellipsoid. This result proves mathematical exist of the parameter ellipsoid, so that a progress to the gravitation problem of double layer ellipsoid is gained.