Baiyuneboites-(Ce) occurs in the REE--Fe--Nb ore deposits at Baiyunebo, Inner Mongolia. As a newmineral--NaBaCe_2,[Fl(CO_3)_4], it is a Na--Ba--REE(Ce-series ) fluor-carbonate The authors haveconducted extensive investigations into the basic mineralogy, mineralogical spectroseopy and X-raycrystallography of the mineral and have elaborately determined its chemical composition. Numerous data onmineralogical experiments and fundamental parameters with respect to its crystal structure have beenobtained. X-ray structural analyses were elaborated. In addition, highi-resolution electron microscopicstudies were performed and its structural image was photographed in order to validate the results of X-raystructural analyses. The experimental data available in conjunction with the comparison hetweenbaiyuneboite--(Ce) and its analogues are sufficiently sensitive to show that haiyuneboite--(Ce) is a new mineral. As a new mineral - NaBaCe_2, [Fl (CO_3) _4], it is a Na - Ba - REE (Ce) -series) fluor-carbonate The authors haveconducted extensive investigations into the basic mineralogy, mineralogical spectroseopy and X-ray crystallography of the mineral and have elaborately determined its chemical composition. Numerous data on mineralogical experiments and fundamental parameters with respect to its crystal structure have beenobtained. X In addition, highi-resolution electron microscopic studies were performed and its structural image was photographed in order to validate the results of X-rays structural analyzes. The experimental data available in conjunction with the comparison hetweenbaiyuneboite - (Ce) and its analogues are substantially sensitive to show that haiyuneboite - (Ce) is a new mineral.