The transition wavelengths, oscillator strength, Einstein An0 and B0n coefficients of excitation of silicon dioxide molecule from ground state to the first five different excited states are calculated by employing density function theory B3P86 and single substitute configuration interaction approach with basis set 6-311G**. The excited states of silicon dioxide molecule under different external electric fields are investigated. It is shown that the HOMO-LUMO gaps become smaller and the electrons of the occupied orbital are more apt be exited to the virtual orbital as the external electric field intensity becomes stronger. Thus the application of the external electric field facilitates the exitation of the SiO2 molecules.