By digital integration, background subtraction and self-deconvolution for SiL2,3VV Auger spectra measured on the cleaved clean Si (111) surface and that with oxygen adsorbed, the partial transition densities of state of clean surface and adsorbed surface are obtained. With reference to other experimental and theoretical results, it could be inferred from these partail transition densities of state that oxygen is adsorbed both in a molecular state and in an atomic state, and in the adsorbed stage the oxide may also be formed.