Xie Douke et al. (1989) determinated the crystal structure of omphacite from the Dabie Mountains. They affirmed that this crystal has space group P2/c, and in its structure, there are two kinds of tetrahedral chain with S-rotation and O-rotation respectively; the four symmetrically unequivalent M-sites are all 6-coordinated octahedra and Al exists in all of them with higher occupancies.A restudy on the data of this structure was carried out by the authors. It reveals that the true space group of the omphacite from the Dabie Mountains is P2/n rather than P2/c; and in its structure, there is only one kind of tetrahedral chain with O-rotation, the O3-O3-O3 chain angle is 170. 02% andM2 and M2(1) sites are of 8-coordination distinguished from 6-one of Ml and M1 (1) sites. In addition, the authors deem that, based on the M-O bond separation, all of Al should enter the smallest M1(1) site, while the site occupation between Al and Mg would be completely ordered. Thus, the structure mentioned above is a typical one of ordered omphacite with space group P2/n, rather than a new type P2/c structure for omphacite.The cause responsible for an incorrect space group is that the selection of the unit cell does not conform to the standard. The authors, therefore, recalculated the unit cell parameters and atom coordinates based on the data given by Xie Douke et al. , and furnish the correct ones here. Although some major errors have been found in the structural explanation given by Xie Douke et al. , the structural data are valuable.