The invention discloses a preparation method of an aluminum alloy coiled material for a tank body. The preparation method comprises the following steps: ingot casting, hot rolling, cold rolling, re-cleaning, finished product annealing, bright rolling and the like. According to the preparation method, by utilizing novel process preparation steps and reasonable parameter settings, the surface brightness of a product can be improved on the premise that mechanical properties of aluminum alloy meet design requirements of a tank car manufacturing factory, the transverse surface chromatic aberration of wide coiled materials/panels and the like can be reduced, and the surface chromatic aberration of different batches of the coiled materials/panels can be reduced; and the procedures of subsequent chemical polishing and the like can be omitted, so that the later-period surface treatment cost can be lowered. Compared with traditional aluminum alloy coiled material production schemes, the preparation method has the advantages that the process can be utilized for producing the aluminum alloy coiled materials/panels for a tank body of a tank car and can meet the requirement of the tank car manufacturing factory on the further reduction of the weight of the tank body as well as the requirement of a tank car customer on the aesthetic sense of the tank car.