A cobalt complex with a three-dimensional supramolecular structure was synthesized through ionothermal method. Its structure was characterized by elemental analysis, FT-IR spectroscopy, XRD and TG. Single-crystal X-ray diffraction studies reveals that the complex is in the tetragonal system, space group P21/c with a=0.943 37(6) nm, b=1.451 5(7) nm, c=1.185 48(6) nm, β=100.051(5)°, V=1.598 37(15) nm3. The complex is composed of isolated anion Br- and ［Co(DINE)2］2+cation, which are held together through the hydrogen bonds, formed a three-dimensional supramolecular structure. Furthermore, its fluorescence property was also studied.