The invention discloses treatment solution for preparing an aluminum alloy surface amorphous composite passivation film, a preparation method and application. A formula of the treatment solution comprises 5 to 15g/L of corrosion inhibiting negative ion-containing rare earth salt, 3 to 10g/L of catalyst type composite oxidant, 1 to 3g/L of auxiliary oxidant, 0.1 to 0.5g/L of buffering film-forming accelerator and 0.5 to 1.5g/L of composite stabilizer. The treatment solution does not contain any toxic chromium or organic substances, does not need heating during conversion treatment of 2 to 5 minutes, and can prepare the golden amorphous 'rare earth-manganese' composite passivation film with excellent performance on the aluminum alloy surface. The treatment solution well solves environmental pollution and human harm caused by the present hexavalent chromium treatment, and can overcome the defects that a zirconium titanate series conversion film is colorless and field judgment cannot be realized. The preparation method has the advantages of simple process, simple and convenient operation and low cost, and is easy to realize industrialization.