The ab initio configuration interaction method and coupled-cluster theory have been used to optimize the possible ground-state structures of SiF2. The method QCISD/6-311G(2df) is most suitable for the calculation of SiF2 by comparing the experimental value and the calculated value; and the calculated equilibrium structure, harmonic frequency, dissociation energy, force-constant are in good agreement with the experimental data. The potential energy functions of SiF2 have been derived from the many-body expansion theory. In the symmetry of stretching vibration and rotation potential energy diagram of SiF2, there is a saddle point in the reaction kinetics SiF+F→SiF2. A stable SiF2 molecule could be formed when F atom with an energy surpassing 4.38 eV. These are completely reported so far as we know for the first time. In addition, it is found that a stable SiF2 molecule could be formed through two equivalent channels of SiF+F→SiF2. And the reaction is endothermic with a threshold energy.