The invention discloses an environment-friendly composite colorful passivating solution and a preparation method thereof and belongs to the technical field of surface treatment of metal materials. Thepassivating solution comprises the components of 17-22 g/L of sodium silicate, 4-8 g/L of sodium molybdate, 6-10 g/L of sodium nitrate, 3-7 mL/L of hydrogen peroxide, 1-3 g/L of potassium fluoride, 2-6 mL/L of nitrilotrimethylene triphosphonic acid, 2-4 g/L of sodium gluconate, 2-4 mL/L of tartaric acid and the balance water, wherein the pH value of the passivating solution is 2.0-2.5. The preparation method of the passivating solution comprises the steps that the sodium silicate, the sodium molybdate, the sodium nitrate, the potassium fluoride, the nitrilotrimethylene triphosphonic acid, thesodium gluconate, the tartaric acid and the hydrogen peroxide are sequentially added into deionized water to be evenly mixed; the water with the constant volume is added to the needed volume; and sulfuric acid is used for adjusting the pH value to be 2.0-2.5, and thus environment-friendly composite colorful passivating solution is obtained. A galvanized layer passivated film treated by the passivating solution is colorful, bright in color, even in film forming and excellent in corrosion resistant performance; the passivating solution does not contain trivalent chromium, hexavalent chromium and other harmful substances and is environmentally friendly, free of pollution, simple in passivating process and high in passivating efficiency, and the corrosion resistance of a film layer is good.