This work aims at developing a new environmental-friendly treatment for hot-dip galvanized (HDG) steel as alternative to the classic systems based on chromates. A double layer film on the HDG steel sheets was prepared by immersing the sheets in 5 g/L Ce(NO3)3 aqueous solution and 5 vol.% silane solution in turn. The morphology of the cerium conversion film was analyzed using scanning electron microscopy (SEM). The corrosion resistance of the films was investigated by linear polarization (LPR) and natural salt spray (NSS) tests. The results show that the surface morphology of cerium conversion film appears on a “dry-mud” structure, which is favorable to enhance the combined strength between the cerium conversion and the silane film. The corrosion protection efficiency of the double layer films increases greatly, especially both the anodic and cathodic processes of zinc corrosion on the samples are suppressed conspicuously, and the synergistic protection effect of the single cerium film and the single silane film is evident.