This paper deals with a fluor-carbonate mineral of Ca-Ba-REE(Ce-series) recently discovered in China by the authors, whose crystalstructure has been thoroughly studied. The data collection was completed on a RASA-5RP auto- matic four-circle single crystal diffractometer in our university (graphite monochromator, Moka, 50kV/150mA, 2θ=2-65º).The cell parameters refined on this device are a=b=5.093(6)A，c=23.017(6)A and V=517A3. 821 reflec- tions were collected, of which 344 show F>3σ(F).The structure was solved by threedimensional Patterson P(uvw) and the differential electron density map using space group P62c, Isotropic refinement led to the value R=0.06 for all 344 independent reflections, and anisotropic refinement to R= 0.05. Atomic coordinates, site occupancies and isotropic thermal vibration parame- ters are given in Table l .The structure has a layered feature(// c axis).All heavy atoms (Ba, Ce) and C03 group form a hexagonal base-centered net-like framework. At z=1/4 and z=3/4 the hexagonal layer consists of Ca and F atoms; in which each kind of atoms is also arranged in a hexagonal. base- centered net-like framework. Those hexagonal layers of atoms are stacked along c axis in the sequence of Ba-Ce-Ca-Ce-Ba…. The plane of CD3 group is normal to c axis.