The tetracyanopyridine (4-cyanopyridine and 3-cyanopyridine) was reacted with rare earth nitrates (Ln=La, Gd, Er) under hydrothermal conditions by the Demko-Sharpless method, and four rare earth tetrazolium ionic compound were synthesized safely and effectively, named ［Ln(H2O)8·3(p-TPD)·2(p-HTPD)·7H2O］, (Ln=La(1), Gd(2), Er(3), p-TPD=4-tetrazolpyridine), ［Ln(H2O)8·3(m-TPD)·6H2O］, (m-TPD=3-tetrazolpyridine, Ln=Er(4)). These four rare earth tetrazolium ionic compounds were characterized by the single crystal X-ray diffraction, infrared spectroscopy, thermogravimetry, dielectric properties, X-ray powder diffraction. The X-ray single crystal structure analysis shows that the four rare earth tetrazolium compounds were all ionic, and the rare earth metal ions and ligands were in two different layers. The ［Ln(H2O)8］3+ structure unit and p-TPD and water molecules formed a cationic layer through hydrogen bonding, while p-TPD and p-HTPD formed an anion layer through π-π stacking and hydrogen bonding. The cation layer and anion layer alternately form a regular network structure. Moreover, the dielectric properties tests indicate that the compounds 1, 2 have good dielectric properties.