The structure optimization and frequency calculation have been carried out at B3LYP/6-31++G** theoretical level，and IR spectrum，Raman spectrum and thermodynamic property at different temperatures have been obtained. The results indicate that the carbon and the oxygen in the —COOH group，and the nitron in —（OS）2—NH group come into formation of different large π bonds with the benzene rings，and there is a dihedral angle of 63.2° because of place blocking and conjugate effect. The first vertical excited state electronic transition energy was calculated by time-dependent density functional theory，and the maximal absorption wavelength was obtained at 312.7?nm，belonging to near UV，which is in good agreement with experimental value of 307?nm in dichloromethane solvent.