Geometry and vibrational frequencies of the ground state of Si2O2 molecule are studied using density function theory (DFT) at the level of cc-pvtz and 6-311++G**.It is found that the optimizing value by B31yp/cc-pvtz is closer to the experimental data.The excited properties under different exteal electric fields are also investigated by the time-dependent-DFT method.Transitions from the ground state of Si2O2 molecule to the first singlet state under different exteal electric fields can take place more easily.The corresponding absorption spectral line is about 360 nm in wavelength and the excitation energy is about 3.4 eV.