In order to decrease the acidity of insensitive explosive 3-nitro-1，2，4-triazol-5-one （NTO）， NTO·（3，5-DATr） energetic ionic salt （Ⅰ） and NTO/IMZ energetic co-crystal （Ⅱ） were prepared by the reactions of NTO with 3，5-diamino-1，2，4-triazole （3，5-DATr） and imidazole（IMZ）. The single crystals were obtained by solvent volatilization， and the crystal structures were measured by single crystal X-ray diffraction. Crystal Ⅰ belongs to monoclinic crystal system， space group P2₁/c， with M_r=229.19，a=3.5687（7） Å，b=17.245（3） Å，c=14.655（3） Å，β=93.79（3）°，V=899.9（3） ų，Z=4，D_c=1.692 g·cm^-3；Crystal Ⅱ belongs to orthorhombic crystal system，space group Pbcn，with M_r=207.17，a=16.9398（16） Å，b=5.6802（5） Å，c=17.9111（19） Å， V=1723.4（3） ų， Z=8， D_c=1.597 g·cm^-3. Differential scanning calorimetry （DSC） and thermal weight loss method （TG） were used to test their thermal decomposition properties， and the results show that both Ⅰ and Ⅱ have good thermal stability. The Gaussian 09 program was used to optimize the molecular structures and calculate their enthalpy of formation. Software EXPLO 5 was used to calculate the detonation velocity and pressure of Ⅰ（D=7662.3 m·s^-1，p=21.0 GPa） and Ⅱ（D=6490.2 m·s^-1，p=14.6 GPa）. The mechanical sensitivity was tested by the BAM method. Results show that both of them are insensitive towards impact and friction （IS > 40 J， FS > 360 N）. The pH value of standard samples were measured by pH meter. The pH values of NTO， Ⅰ， and Ⅱ in 0.01 mol·L^-1 standard solution are 2.92 （22.8 ℃）， 4.10 （22.7 ℃）， and 4.98 （22.8 ℃）， respectively， indicating that the formation of salt and co-crystal significantly decrease the acidity of NTO.