A new inorganic-organic hybrid,[DMAPM]+[CdI3]-(DMAPM+ = p-dimethyla-mino-1-methyl-pyridinium),has been synthesized by the reaction of [DMAPM]+I-and CdI2,and characterized by IR and elemental analysis.The crystal structure was obtained via X-ray single-crystal diffraction with the following data: triclinic,space group P1,a = 8.0974(9),b = 9.6187(10),c = 10.5028(8)(A),α = 75.049(6),β = 86.321(3),γ = 87.791(3)o,V = 788.50(13)(A)3,Dc = 2.655 g/cm3,Z = 2,R = 0.0385 and Wr = 0.0976.In the structure,one cadmium and four iodine atoms form a tetrahedral geometry,and two of such tetrahedra are connected in a co-line way to constitute Cd2I62-dimer.To our knowledge,this is the first example of dimerized CdI4 tetrahedron.All of the dimers are packed in the same mode,while the [DMAPM]+ cations are anti-parallelly arrayed.