Abstract: In this paper, the density functional theory (DFT) is used to optimize the stable configuration of C₃F₆O molecule at the B3LYP/6-311G+(3d, 3p) level, and the ground state energy, dipole moment, frontier orbit, infrared spectrum, and Raman spectrum of C₃F₆O molecule under an external electric field are calculated. On this basis, using the time-dependent density functional theory at the 6-311G+(3d, 3p) basis set level, the excitation energy, transition wavelength and oscillator strength of the first 10 excited state of C₃F₆O molecule under the action of an external electric field, the excitation characteristics, UV-visible spectra, etc. are studied, and the main excited state are analyzed by hole electron theory. The research results indicate that an external electric field can change parameters such as molecular energy, dipole moment, and excitation energy. When the electric field range is (0~0.07 a. u.), the structure and characteristics of C₃F₆O molecules vary significantly with the electric field intensity; When the applied electric field gradually increases, the total energy of C₃F₆O molecules gradually decreases, but the dipole moment undergoes opposite changes; HOMO-LUMO both decreased. As the external electric field gradually increases, the infrared spectrum of C₃F₆O molecule exhibits a red or blue shift, and the molar absorption coefficient redistributes. An external electric field can change the excitation characteristics of molecules, and as the external electric field increases, the excitation energy of molecules decreases, making it easier to excite.