The geometries of polynitropyridines have been fully optimized at the level of B3LYP/6-31++G^**. The electronic structures,the molar volumes,and the standard molar thermodynamic functions for these polynitropyridines have been calculated at the same level. Calculated results show that the C—N bonds in the pyridine ring shorten as —NO₂ groups are introduced into the 2 and 6 sites of pyridine ring and change slightly as the 3 and 4 positions are occupied by —NO₂ groups and the 2 and 6 positions by —NH₂ groups. For polynitropyridines the introduction of —NH₂ group can increase the bond order of the neighboring C—NO₂ bond. At the B3LYP/6-31++G^** level,Mulliken population analysis is not suitable for the calculation of atomic charges of polynitropyridines,but natural population analysis can be applicable for it. For 3,5-diamino-2,4,6-trinitropyridine the predicted density reaches 2.2 g ·cm^-3,and the smallest bonder order of C—NO₂ bonds is slightly smaller than that of DATB,implying that 3,5-diamino-2,4,6-trinitropyridine is a high density,low-sensitive explosive.