Abstract: This study investigated the effects of external electric fields (-0.04 a.u. to 0.04 a.u.) on the bond length, total energy, dipole moment, energy gap, infrared (IR) spectrum, and potential energy surfaces of NO molecules using density functional theory (DFT) at the B3LYP/D95(3df, 3pd) basis set level. Furthermore, the excited-state properties of the molecule were analyzed using the CIS-B3LYP/D95(3df, 3pd) method. The results demonstrate that the ground-state properties of the molecule are significantly influenced by the external electric field. As the external electric field increases from -0.04 a.u. to 0.04 a.u., the total energy first increases and then decreases, while the dipole moment initially decreases and subsequently increases, while the energy gap progressively widens. The charge population numbers around the O and N atoms continuously increase. The harmonic vibrational frequencies and IR intensities exhibit substantial variations under external electric fields, indicating that the IR intensity can be modulated by electric fields. Additionally, the external electric field affects the excitation energy, excitation wavelength, and oscillator strength of the NO molecule, suggesting that the excited-state properties of NO can be effectively regulated through external electric field manipulation.