The invention provides an aluminum alloy for an automobile body and a preparing method of the aluminum alloy and relates to the technical field of component design and heat treatment of aluminum alloys used for covering parts of automobile bodies. The aluminum alloy for the automobile body comprises, by weight percent, 0.7%-1.2% of Mg, 0.4%-0.8% of Si, 0.2%-0.9% of Cu, 1.5%-3.0% of Zn, smaller than or equal to 0.5% of Fe, 0.02%-0.06% of Sn, 0.02%-0.06% of In and the balance Al. Due to the fact that chemical components are limited and optimized, the aluminum alloy for the automobile body has higher room temperature stability, and therefore the baking varnish capability of the downstream part of the aluminum alloy for the automobile body can be obviously improved. In addition, the preparingmethod of the aluminum alloy for the automobile body includes the step that an aluminum alloy raw material is smelted into a blank, and the chemical components of the blank are controlled to meet theabove requirement. By means of the preparing method, the production process is shortened, the cost is reduced, and the preparing method is suitable for industrial application and popularization.