Structures of hematite(${alpha}$-Fe2O3), Ba-ferrite(BaFe12O19) and Zn2Y(Ba2Zn2Fe12O22) were studied by powder X-ray diffraction(XRD) method. Powder XRD patterns of the ferrites were analyzed with the Rietveld method, and the final refined R-factors were RWP<0.01 and RI<0.03. The lattice parameters refined with hexagonal crystal system were a=5.0342${AA}$, c=13.746${AA}$ for hematite, a=5.8928${AA}$, c=23.201${AA}$ for Ba-ferrite, and a=5.8763${AA}$, c=43.567${AA}$ for Zn2Y. In the hematite, the oxygen parameter is 0.3072 and the Fe-O distances in FeO6octahedron are 1.941${AA}$ and 2.118${AA}$, close to the single crystal data of Blake et al.. In the Ba-ferrite, the Fe atom in oxygen trigonal bipyramid is displaced 0.155${AA}$ away from the BaO3 mirror plane into 4e position. In the Zn2Y, 75% of Zn is located at the oxygen terahedral site in S-block.