Abstract: We calculated the excitation energy, wavelengths, oscillator strength of CH3—C2H3O molecule from ground state to the first ten different excited states by using the method of density functional theory B3P86 and timedependent density functional theory (TDDFT) at the basis sets 6311++G(2df), and investigated the excited states of CH₃—C₂H₃O molecule under different external electric fields. The results show that the excitation energies of the first ten excited states of CH₃—C₂H₃O decrease sharply with the increase of the external electric field. The molecules  are easy to be excited and dissociated under the external electric field.

Key words: propylene oxide, excited state, electric field, timedependent density functional theory (TD-DFT)