IR spectra of polynitroadamantenes were obtained by vibrational analysis based on fully optimized molecular geometries and electronic structures obtained at B3LYP/6-31G^* level and assigned. Compared the calculating IR spectra with that of experiments known,all the IR obtained in this paper were considered to be reliable. Based on the frequencies scaled by 0.96 and the principle of statistic thermodynamics,thermodynaminc properties were evaluated. The relationships of thermodynamic functions with temperature and the number of nitro group were discussed,and it was found that the latter shows a good group additivity rule.