Abstract Huanghoite, BaCe [Fl(CO3)2], a new mineral from China, is a kind of carbonate containing Ba, Ce, F. It belongs to trigonal system. The intensity data are collected with the aid of fully automatic four-circle X-ray diffractometer. The lattice parameters are α=b=5.070(±0.003?), c=38.408(±0.005?); space group is R3m; z=6. More exact determination has been made on the basis of earlier worke, giving the final R=0.041.The relation between superstructure and pseudo-structure of this crystal has been analysed. We compared our results with that of earlier works. Suggestion is made for the correction for similar minerals. Finally, the individual experimental data are discussed.