The work aims to solve the problem of environmental pollution caused by hexavalent chromium passivation process on the surface of hot galvanized steel sheet. A kind of new and environment-friendly chromium-free composite passive solution was prepared, which was mainly made from ammonium molybdate, nano silica sol, tannic acid, silane coupling agent KH151 and KH792. Microscopic morphology, elemental composition and chemical composition of the chromium-free composite passive film were analyzed by SEM, EDS and XPS. The effects of Mo on corrosion resistance of galvanized sheet were tested by electrochemical workstation, and corrosion resistance of the film at different weight was studied by performing neutral salt spray test. Mo element in the chromium-free composite passive film could inhibit generation and development of microcracks, prevent corrosive mediums from spreading toward metallic substrate, and improve resistance of the composite silane film. Electrochemical impedance of the composite passivation film was 1.6 times higher than that of the silane passive film (close to that of Cr6+ passive film), which could inhibit corrosion electrochemical reaction, reduce reaction speed and strengthen corrosion resistance of the film. In addition, corrosion resistance was comparable with that of Cr6+ film as the film reached 892 mg/m2 and corrosion area was 0; and the corrosion resistance was excellent as the film reached 1252 mg/m2. The chromium-free composite passive film combines the advantages of both silane passivation film and molybdate passivation film, compactness and combinability are better, and corrosion resistance of the film is close to/achieves the effect of hexavalent chromium passivation.