Analytic local potential energy surfaces for S2O in the ground state and the excited states were calculated at MRCISD and MRPT2 levels. Further, the data points selected were fitted to a polynomial force field and the calculations for the interaction of vibration configuration were carried out. Then, the analyses of normal vibration modes and vibration energy levels were performed. The local potential energy surfaces were improved by adjusting a few force constants. The mean-square roots of the deviation between computed and available experimental vibration spectra for the ground state and the excited state are 3852cm-1 and 644cm-1, respectively.