A Si-covered 6H-SiC(0001) surface was transformed from a Si-rich to C-rich one with increasing annealing temperature. An alkali metal is well known for promoting oxidation. We studied the oxidation to Cs pre-adsorption on a 6H-SiC(0001)-(3×3) reconstructed surface using metastable-induced electron spectroscopy (MIES), ultraviolet photoelectron spectroscopy (UPS), and low-energy electron diffraction (LEED). The (3×3) reconstructed surfaces was adsorbed Cs and exposed oxygen at room temperature. The MIES results show that the intensity of electron emission induced Cs6s increased with Cs evaporation. For the oxygen-exposed Cs/SiC surface, the emission intensity of the Cs6s-induced peak rapidly decreased and a dissociated adsorption oxygen-induced peak appeared. When the oxygen-adsorbed Cs/SiC(0001) surface was annealed until 800°C, Cs atoms were desorbed from the surface and O bonded with Si, forming SiO2.