Abstract: Using density functional theory at the B3LYP/6-311G(d, p) level, we calculate the changes in the properties of the arsenic trichloride molecule under external electric fields ranging from -0.02 a.u. to 0.02 a.u. As the electric field changes, the bond length of the 1As-4Cl bond in the AsCl₃ molecule deereases gradually; the total energy increases trend; the dipole moment decreases trend; the energy gap decreases; the charge distribution changes; blue shift phenomenon occurs in the infrared spectrum; the Raman spectroscopy exhibits a red shift in the low frequency range and a blue shift in the high frequency range; As the external electric field increases, the molecular potential barrier gradually decreases, when the electric field strength reached 0.03 a.u., the molecule dissociates along the 1As-4Cl bond. Furthermore, using time-dependent density functional theory at the CAM-B3LYP/6-311G(d, p) level, the impact of the external electric field on the excited-state properties and electronic transitions is studied. The findings indicate that the external electric field significantly affects the properties and behavior of the arsenic trichloride molecule. This research provides important insights into the degradation processes of arsenic trichloride molecules under external electric fields.