A chrome-free chemical conversion coating was prepared using stannous sulfate as the main salt. The morphology of the chemical conversion surface layer was observed by scanning electron microscopy (SEM). Coating composition and the microcosmic phase structure were characterized using energy dispersive X-ray (EDX) analysis and X-ray diffraction (XRD) respectively. Electrochemical method and dropping test were used to study the coatings corrosion resistance. The results indicated that the tin salts conversion coating is a crystal structure material that composites with Sn-F-O-Al et al., the surface appears as a accumulation of spherical particles, the crystallinity of conversion coating is better than uncoated sample obviously, the corrosion resistance has improved too.