Abstract: It is necessary for precise ephemeris to be interpolated in high-precision satellite positioning data processing. In this paper,based on the sliding Lagrange interpolation method,it is investigated that the relationship between the interpolation order and the interpolation accuracy of three kinds of Beidou satellites in BeiDou precision ephemeris respectively. The example shows it is different that the interpolation order of the three kinds of BeiDou satellites to achieve the best interpolation precision; as long as a reasonable order is adopted,three kinds of satellites can all achieve millimeter interpolation precision. This method can be better applied to the interpolation of the precision ephemeris of the BeiDou satellite，and this method is completely suitable for interpolating the precision ephemeris of the BeiDou satellite.