Based on an overall review of the research achievements and the problems of rare earth metal conversion coatings for aluminum alloys at home and abroad and combined with our early study of aluminum alloy’s inhibition mechanism and coating formation mechanism, this paper studied the chemically formed cerium conversion coatings on aluminum alloys with the aid of oxidation accelerator. The morphology and the structure and the composition of rare earth metal conversion coating were investigated by scanning electron microscope (SEM) and X-ray energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results show that rare metal conversion coating on B95 surface formed by Ce(III) is mainly composed of Al and the Ce oxides, the Ce oxides are mainly made up of Ce(IV)(CeO2 and Ce(OH)4 compounds. During the whole process, Ce is distributed evenly; the conversion coating is compact and even. Some deposits rich in Ce stay locally. The conversion coating is non-crystal structure. The mechanism of the corrosion resistance of the coating was studied by electrochemical methods together with scanning electron microscope (SEM) and X-ray diffraction (XRD). The results indicate that H2O2 helps to make the conversion coating on the B95 surface becoming more compact and non-crystal structure , it is able to prevent water and Cl+ from permeating the conversion coating, it will inhibit simultaneously both the cathodic and anodic reactions of corrosion on the alloy surface. The rare earth conversion coating still retains the self-rehabilitation ability after pitting.