The paper aims to hinder the appearance of white rust on the hot-dip galvanized sheet and improve corrosion resistance of galvanized sheet. An organic-inorganic composite passivation film with an aqueous solution of shellac was prepared by orthogonal test. Tafel polarization curve measurement, AC impedance spectroscopy (EIS), lead acetate dripping corrosion test and neutral salt spray test were used to compare and analyze the corrosion resistance of the galvanized layer and chromate passivation plating of matrix, silicate + shellac composite passivation. The adhesion properties of the substrate and the chromium-free passivation sample were tested by the friction method. The morphology and structure were analyzed by scanning electron microscopy, X-ray photoelectron spectroscopy and infrared spectroscopy. The results showed that the surface of the composite passivation film with added aqueous solution of shellac was flat and dense; and the corroded area was less than 10% for the composite film after 72-h NSS test. The lead acetate test and electrochemical test showed that the corrosion resistance of the composite passivation film was better than that of the substrate. The adhesion test showed that the composite passivation film had good adhesion. It can be seen from the test results that the shellac and silicate in the composite passivation solution are interwoven into O—Si—CH2 structure, and a dense film layer is formed on the surface of the galvanized layer by bonding with metal ions, making the composite passivation film dense and flat. And the corrosion process is strongly suppressed.