Abstract This paper addresses the reason why a geocentric coordinate system is adopted for us, and expounds the definition and realization of the China Geodetic Coordinate System 2000（CGCS2000） and compares it with WGS84. The CGCS2000 is a geocentric system adopting the GRS80 ellipsoid, and is realized by coordinates and velocities at epoch 2000.0 of the points of the national GPS geodetic network 2000. It is consistent with ITRF and compatible with WGS84.
