A density functional method(B3LYP) with 6-311++G(3df, 3pd) basis sets has been used to study the equilibrium geometric parameters, total energies, dipole moments, charge distributions, the highest occupied molecular orbital(HOMO)energies, the lowest unoccupied molecular orbital(LUMO)energies, energy gaps of CHF=CHF under different external electric field ranging from -0.05 to 0.05 a.u. On the basis of optimized configuration, the excitation energy, transition wavelength and oscillator strength in the same intense external electric field and basis sets are calculated by the configuration interaction singles(CIS-B3LYP) method. The results show that the geometric parameters of CHF=CHF molecule strongly depend on the magnitude and direction of external electric field. The total energy of CHF=CHF molecule in different external electric fields ranging from -0.05 a.u. to 0.05 a.u. first increases and then decreases. On the contrary, the dipole moments of CHF=CHF first decrease and then increase. The HOMO energy is found to decrease,while LUMO energy first increases and then decreases through the variation of the external field.The energy gaps of CHF=CHF first increase and then decrease. The excitation energies, transition wavelengths and oscillator strengths are very complicated with the change of the external electic field.