Abstract: The dioxane complexes of cerium(Ⅳ), Ce(C₄H₈O₂)₄Cl₄ or HCe(C₄H₈O₂)₄Cl₅ were prepared by gradually dissolving dried cerium (Ⅳ) hydroxide in dioxane (C₄H₈O₂)and then saturating with dried HCl gas. The formed solid complex was mixed with nitrogen-containing compounds (L), resulting a series of new complexes of ammonium pentachlorocerate (Ⅳ) (H L) Ce (C₄H₈O₂)_xCL₅ (L=8-hydroxy quinoline, imidazole,o-phenanthroline,pyridine, β-naphthoquinoline,phenazine; x=1,2,3,4). The complexes were characterized by elemental analyses, infrared spectra, ultra-violet spectra,thermal analysis and photoelectron spectra. The effects of the variety of nitrogencontaining li-gands on the thermal stabilities of the complexes bave been primarily studied.