The equilibrium geometry of SiO and SiO2 molecule has been calculated on the computational levels of density functional theory (DFT). The possible electronic state and reasonable dissociation limit for the ground state of SiO and SiO2 X1A1 molecule are determined based on atomic and molecular reaction statics. And Murrell-Sorbie analytic potential energy function of SiO molecule has been derived through the least-square fitting to ab initio data. Similarly, the harmonic frequency has been calculated, and the analytic potential energy function of SiO2 molecule has been derived using many-body expansion theory.