Isonicotinato cadmium(II) complex [Cd(C 6 H 4 NO 2 ) 2 (H 2 O) 4 ] has been synthesized by hydrothermal method and characterized by elemental analysis, electronic-spectra and thermogravimetric analysis. Density functional theory (DFT) method calculations of the structure, atomic charges distribution, electronic spectra, natural population analysis and the thermodynamic properties at different temperatures have been performed. The calculated results show the electronic transitions are mainly derived from the contribution of bands π → π * and the decomposition of the title compound should first occur at the bond of Cd O, then at the bond of Cd N, which agrees very well with the experimental data.