In order to explore the variation rule of explosives′ sensitivity in the external electric field, the bond lengths, nitro charges, bond dissociation energies of the potential trigger linkages and the impact sensitivities, electrostatic spark sensitivities as well as shock initiation pressures of the 1,4-dinitroimidazole-N-oxide (1,4-DNIO) explosive were investigated by the B3LYP/6-311++G(2d,p) and M06-2X/6-311++G(2d,p) levels of theory. Results show that the N─NO₂ bond is the most likely trigger linkage in the initiation reaction of explosive, followed by N→O, and finally the C─NO₂ bond in the external electric fields and the absence of the electric fields. Under the external electric fields along the positive directions of the N→O and C─NO₂ bond axes as well as the negative direction of the N─NO₂ bond axis, the dissociation energies of the N→O and C─NO₂ bonds are decreased, while those of N─NO₂ bond are increased, leading to the increases of the H₅₀ values and thus the decreases of the impact sensitivities. The opposite conclusion is drawn when the explosives are in the external electric fields with the reverse directions against the above cases. The changes in the bond lengths (ΔR), electron density values (Δρ), nitro charges (ΔQ), bond dissociation energy (ΔBDEs) of the trigger linkages and thoes in the impact sensitivities (ΔH₅₀) show good linear relationships withthe external electric field strengths, respectively. In most cases, the values of correlation coefficient R² are larger than 0.9500. The external electric fields have little effect on the electrostatic spark sensitivities or shock initiation pressures, accompanied by the variations lower than 0.5 J and 0.15MPa with the field strengths from –0.0010 a.u. to 0.0010 a.u., respectively.