The dielectric constant (DC) is one of the key properties for detection of threat materials such as Improvised Explosive Devices (IEDs).In the present paper,the density functional theory (DFT) as well as ab-initio approaches are used to explore effective methods to predict dielectric constants of a series of 12 energetic materials (EMs) for which experimental data needed to experimentally determine the dielectric constant (refractive indices) are available.These include military grades energetic materials,nitro and peroxide compounds,and the widely used nitroglycerin.Ab-initio and DFT calculations are conducted.In order to calculate dielectric constant values of materials,potential DFT functional com-bined with basis sets are considered for testing.Accuracy of the calculations are compared to experi-mental data listed in the scientific literature,and time required for calculations are both evaluated and discussed.The best functional/basis set combinations among those tested are CAM-B3LYP and AUG-cc-pVDZm,which provide great results,with accuracy deviations below 5％ when calculated results are compared to experimental data.