The surface morphology of the SiOx film grown on 4H-SiC by thermal oxidation was observed by scanning electron microscope (SEM) and atomic force microscopy (AFM), respectively. The characteristics of the SiOx film and the interface of SiOx/4H-SiC were studied by X-ray photoelectron spectroscopy (XPS). The Gaussian fitting of Si2p, O1s and C1s XPS energy spectra and the corresponding binding energy were analyzed. The composition variances of the SiOx film were also researched with XPS measurement on the different depths. It is expected to find out the chemical composition and state of the SiOx film grown on 4H-SiC by thermal oxidation, and obtain the characteristics of the SiOx/4H-SiC interface.